Britain faces a 'coalition of chaos' under Ed Miliband and Nicola Sturgeon, David Cameron warned today. The Prime Minister, who travelled to Glasgow this morning to unveil the Tory Party's Scottish manifesto, accused the SNP and Labour of posing a 'clear and present danger' to Britain. He said the two parties were pretending to 'slug it out' ahead of next month's poll – but insisted they were both working to ramp up spending regardless of the deficit. Scroll down for video . The Prime Minister, who travelled to Glasgow this morning to unveil the Tory Party's Scottish manifesto, accused the SNP and Labour of posing a 'clear and present danger' to Britain . Mr Cameron said Ed Miliband could now only become Prime Minister with the support of the SNP. He told activists: 'We meet here in Scotland in the middle of a massive political fight. We've got Labour and the SNP on opposite sides – slugging it out – but if you take a step back they're really on the same side. 'You have a weak Labour party, who want more spending, more borrowing, more debt and more taxes. And the people who will prop them up, the SNP – who want even more spending, more borrowing, more debt and more taxes.' Mr Cameron said together, the SNP and Labour 'pose a clear threat to the future of our United Kingdom', adding: 'A coalition of chaos.' He said: The SNP acting as the chain to Labour's wrecking ball, running right through our economic recovery - and it will be you who pays the price. With jobs losses, massive tax rises and an economy back on brink of bankruptcy.' Mr Cameron's blistering attack comes ahead of tonight's live TV election debates between the main 'challenger' parties - including Mr Miliband and Ms Sturgeon, alongside the leaders of Ukip, the Greens and Plaid Cymru. Mr Cameron walks with the leader of Scottish Conservatives as they launch the Tories' election manifesto today . David Cameron and Nick Clegg are not taking part because they have been in power for the last five years. Mr Miliband is expected to use the BBC debate to issue a warning to Scottish voters that success for the SNP north of the border could deliver a Conservative government in Westminster. The Labour leader has ruled out a formal coalition with the SNP in a hung Parliament, but he is likely to face calls from Ms Sturgeon to join a 'progressive alliance' to bring an immediate end to austerity, which is also backed by Plaid and the Greens. Nicola Sturgeon has called on Ed Miliband to work with the SNP to 'lock out' David Cameron from Number 10 . Conservatives are hoping that the debate would give added bite to their claim that a Miliband administration would be 'in the pocket' of the SNP. Tory deputy chief whip Greg Hands said: 'Will we see the alternative to David Cameron in the Challengers Debate? A Frankenstein coalition to bankrupt and break up Britain.' Mr Clegg, who was campaigning in the north-west, said he asked to take part in the debate, but was 'denied the opportunity' by broadcasters. The Liberal Democrat leader told LBC radio: 'David Cameron, I know, didn't want to participate in it, but I don't see why I should have been denied the opportunity to put the side of the story of what the coalition government has done, even if he didn't want to. 'I find it very odd that the debate tonight doesn't have anybody from one of the parties that have actually been trying to govern our country.' Ms Sturgeon said the debate was 'a fantastic moment of opportunity to deliver the positive change that people are looking for'. 'The SNP will be a positive and constructive voice at Westminster, ready to join others in a progressive alliance to end austerity and protect vital public services like the NHS.' Calling on Mr Miliband to 'change direction', Ms Wood said: 'We're calling for an end to austerity and instead balancing the books through job creation and infrastructure investment. 'It's time weapons of mass destruction were confined to history and we divert funds to improve standards of living and prospects for people.' In the debate, each of the five leaders will be allowed a short opening statement before Dimbleby invites questions from 200 voters. Mr Miliband will be positioned to the far left next to Ms Wood and Mr Farage to the far right next to Ms Sturgeon with Ms Bennett in the middle of the group. The 90-minute programme will cover five subjects. Each question will see one-minute opening statements followed by 10 minutes of free debate.
The PM said the SNP and Labour presented a 'clear and present danger' He said the two parties were 'really on the same side' in the election . Mr Cameron said Ed Miliband can only become PM with the SNP's support . Comes ahead of tonight's live TV debate between the main 'challengers' Mr Cameron and the Lib Dem leader Nick Clegg will not take part .