The SNP and Labour have been proved wrong on the economy, on jobs and their support for lighter regulation of the banks, and only the Liberal Democrats can keep British politics on a steady course, Scottish leader Willie Rennie will say today.

Mr Rennie will urge voters not to let the SNP and Labour make the "same mistakes" again by setting up a post-election alliance at Westminster.

He said: "The SNP are climbing on with Labour. They want to borrow even more than them.

"Like Labour, the SNP argued for lighter regulation for the banks - just before they went bust.

"Like Labour, the SNP said that the UK Government's economic plan would fail - just before the economy started to grow again.

"Now, just like Labour they think the answer to high levels of debt is even more debt.

"The SNP were wrong on the banks, wrong on the economy, wrong on jobs - and just like Labour they have the audacity to say that's all in the past and they are definitely right this time.

"Their plan will put the economy at risk all over again. The same mistakes and we should not let them do it."

He will add: "The Tories are hellbent on some ideological drive to reduce the size of the state, cutting so far that our schools, hospitals and colleges are under real threat.

"Labour, who seemed not to have learnt the lessons of the last time they were in government, want to borrow billions more even though debt levels are at a record high.

"That is the threat Britain faces. It's a serious threat. The return to the see-saw economics that has damaged our country in the past.

"David Cameron and George Osborne at one end and Ed Miliband and Ed Balls at the other.

"One end cutting recklessly, the other borrowing recklessly.

"All four damaging the steady, fair economic recovery that our party alone can promise.

"And the SNP, they are climbing on with Labour. They want to borrow even more than them.

"It is a combination of fairness and economic progress that Liberal Democrats bring to government."