Former Prime Minister Sir John Major (left) will today ignore warnings from his former Scottish Secretary against talking up the threat posed by the SNP . David Cameron's campaign attacks on the SNP risk undermining the future of the United Kingdom, senior Conservative peer Lord Forsyth has claimed. The former Scottish Secretary said talking up the threat posed by the Scottish nationalists was 'short-term and dangerous'. The stark warning came as the former prime minister John Major launched a stinging attack on the threat posed by an SNP. Sir John will say a Labour deal with the separatists would mean higher taxes, more debt and fewer jobs - as well as another independence referendum. David Cameron yesterday warned that the prospect of a deal between Ed Miliband and Nicola Sturgeon was 'a match made in hell for the British economy' after the SNP unveiled its manifesto in Edinburgh yesterday. The extraordinary manifesto launch by SNP leader Nicola Sturgeon included massive spending increases, new taxes, more welfare and the end of Britain's nuclear deterrent. Treasury analysis suggests the package would cost taxpayers £148billion over five years. Sir John, who is the last Tory to win an election outright, warned that Ed Miliband would face a 'daily dose of blackmail' from Miss Sturgeon, whose party may win 50 Commons seats. The former PM said: 'If Labour were to accept an offer of support from the SNP, it could put the country on course to a government held to ransom on a vote-by-vote basis. 'Labour would be in hock to a party that – slowly but surely – will push them ever further to the left. And who would pay the price for this? We all would. We would all pay for the SNP's ransom in our daily lives – through higher taxes, fewer jobs, and more and more debt.' Sir John (pictured at a Tory campaign rally today), who is the last Tory to win an election outright, said Ed Miliband would face a 'daily dose of blackmail' from the SNP's Nicola Sturgeon . Senior figures in Ed Miliband's (right) Labour party have appeared to soften their stance on a potential deal with the SNP and Nicola Sturgeon (left) in a hung parliament. It comes after Miss Sturgeon vowed to end austerity . Ed Miliband today accused David Cameron of 'playing fast and loose' with the future of the Union by talking up the threat posed by the SNP. The Labour leader said the Prime Minster was 'threatening the integrity of the United Kingdom' for his own political gain. He insisted there would be no coalition with the SNP and denied Nicola Sturgeon's party would hold the whip hand on policy. He told BBC1's Breakfast: 'A Labour government led by me, what happens in that Labour government will be decided by me, not by the SNP.' Labour had 'fundamental differences' with the SNP, such as the nationalist party's desire for a second independence referendum within five years, he said, adding: 'I'm not having that.' Mr Miliband said Mr Cameron had been 'talking up' the SNP in the hope that it would take votes and seats from Labour north of the border and allow him to 'crawl back' into 10 Downing Street. 'I think David Cameron is playing fast and loose with the United Kingdom,' said the Labour leader. 'This is somebody who has given up hope of winning a majority. He is trying to boost the SNP. 'I think David Cameron is now threatening the integrity of the UK with the games he is playing. And I think Conservatives are now ashamed of what he is doing.' Sir John added: 'The SNP's driving ambition is an independent Scotland and – as the price for their support – they will demand policies that favour Scotland. That is no way to run a country, and nor is it remotely fair to England, Wales and Northern Ireland. 'This is a recipe for mayhem. At the very moment our country needs a strong and stable government, we risk a weak and unstable one – pushed to the left by its allies, and open to a daily dose of political blackmail.' But the Tory tactic of talking up the threat posed by the SNP was slammed by Sir John's former Scottish Secretary Lord Forsyth last night. The Tory peer said: 'We've had the dilemma for Conservatives, which is they want to be the largest party at Westminster and therefore some see the fact that the nationalists are going to take seats in Scotland will be helpful. 'But that is a short-term and dangerous view which threatens the integrity of our country.' He said Mr Cameron's call for 'English votes for English laws' in the aftermath of last year's Scottish independence referendum vote had 'shattered the unionist alliance against the break-up of the United Kingdom'. Yesterday, senior Labour figures appeared to soften their stance on a potential deal with the SNP in a hung parliament. Shadow Chancellor Ed Balls and health spokesman Andy Burnham said the party would be prepared to talk to Miss Sturgeon to try to win backing for a legislative programme. Asked to rule out any arrangement with the SNP after May 7, Mr Balls replied: 'We'll have to wait and see what the election result is going to be.' In a BBC interview, Mr Miliband denied the SNP would dictate policy but again refused to rule out negotiating for support in major Commons votes. Asked if the SNP would be calling the shots, Mr Miliband said: 'That ain't gonna happen. That ain't gonna happen.' Miss Sturgeon used her manifesto launch in Edinburgh to seek to assuage the fears of voters in the rest of the UK about her party being involved in the next government. 'I hold out the hand of friendship,' she declared. Miss Sturgeon said her number one priority would be an end to austerity, vowing to make Scotland's voice heard 'more loudly than it has ever been before'. She said she wanted a 'modest' increase in Government spending to 'make life better for ordinary people across these islands'. She also backed Labour's proposed tax rises. Spending spree wishlist... paid for by England! The Scottish Nationalists yesterday listed their demands for propping up a minority Labour government. JAMES SLACK examines the consequences for the rest of the UK: . DEBT . SNP leader Nicola Sturgeon is pictured launching the Scottish National Party manifesto at the Edinburgh International Climbing Arena yesterday . DEMAND: The SNP's key demand is an end to austerity. Cuts would be replaced with a minimum increase of 0.5 per cent above inflation for five years. NHS spending would rise by £24billion across the UK to deliver a £2billion increase in Scotland. COST: The additional borrowing, which will fall overwhelmingly on English taxpayers, will be £148billion over five years, according to Treasury analysis. HIGHER TAXES . DEMAND: The SNP wants a 50p top rate of tax, a mansion tax and a new tax on bank bonuses. This wish list is identical to Labour's and would form the basis of any post-election deal. Ominously, the manifesto talks of releasing 'additional resources by backing a series of revenue raising measures'. COST: Even though Scotland has very few £2million-plus homes, the SNP still wants a large chunk of mansion tax proceeds to go north. Alex Salmond warns the SNP would try to amend a Labour budget to introduce 'progressive tax measures' that would further clobber the middle classes. THE UNION . DEMAND: The SNP would end the convention under which its MPs do not vote on English-only matters in order to limit private sector involvement in the NHS, repeal Tory health reforms and help Labour force through tuition fee changes. COST: The damage to the Union caused by Scottish Nationalists foisting policies on the English which have no impact on their constituents (the Scots NHS is Scottish-run) could be irreparable. MORE BENEFITS . DEMAND: Reinstate subsidy paid to housing benefit recipients with a spare room. Increase handouts at least in line with the higher CPI rate of inflation. Scrap Universal Credit. Block plans to cut Disability Living Allowance by £3billion. COST: Scrapping the spare room subsidy will cost £470million. Axing Universal Credit would reverse a reform intended to break the culture of welfare dependency that became entrenched under Labour. TRIDENT . DEMAND: Scrap Britain's nuclear deterrent, saving £100billion over the next 35 years. COST: Failing to renew Trident would leave Britain's defences – and standing in the world – hugely diminished at a time of great global insecurity. VERDICT: . For all the bluster and denials, shared policies on tax and benefits provide the basis for a messy and hugely expensive deal between Labour and the SNP on a vote-by-vote basis. Key question is just how much extra borrowing Ed Miliband would be prepared to offer. Expect the markets to go into fright and the pound to slump. He may have been snubbed by his party for its manifesto launch but Alex Salmond has clearly been making an impression elsewhere during the campaign. The former SNP leader, 60, still hopes to emerge as one of the most powerful figures at Westminster in the next Parliament and has been busily electioneering in Gordon – the Aberdeenshire seat he is favourite to prise from the Liberal Democrats. And he gave his profile a boost by taking time out for this bizarre photo opportunity, which involved jumping up and down on a mattress in Port Elphinstone, Inverurie. Mr Salmond was joined by teenager Lewis Wilson. The oddly dressed 16-year-old had been planning a stunt leap on to the mattress from his bedroom window. Former SNP leader Alex Salmond, 60, gave his profile a boost by taking time out for this bizarre photo opportunity, which involved jumping up and down on a mattress with a teenager in Inverurie, Aberdeenshire .
Tory peer and former minister Lord Forsyth warns against SNP attacks.
He says the talking up the SNP threat undermines future of the UK.
Comes as John Major warns a Labour-SNP alliance will cause chaos.
He said Labour propped up by SNP would mean high taxes and fewer jobs.
A ComRes poll for ITV News last night found the majority of the British public – 54 per cent – do not want Miss Sturgeon to play a role in the next government. Some 59 per cent do not want the SNP involved at all.