WILLIE Rennie has unveiled a radical plan for an across-the-board rise in income tax to pay for the biggest investment in Scottish education in a generation.

The leader of the Scottish Liberal Democrats challenged Nicola Sturgeon to back his party's plan, which he said would raise almost half a billion pounds and "save Scottish education".

The party’s proposals will include a Pupil Premium - meaning schools receive extra cash for every student from a deprived background - as well as an expansion in nursery education, a reversal of college cuts and stopping school cuts.

As the plan would mean a blanket 1p rise across all income tax bands, Holyrood would have the power to implement the scheme from April rather than waiting for new powers under the Scotland Bill to arrive. The Liberal Democrats will submit the proposal as part of the Scottish Government's budget process, but if they are rejected, will go into May's Holyrood election with the plan as a flagship policy.

A party source said that with the SNP threatening to scupper the new powers as negotiations continue over the financial deal underpinning the Scotland Bill, Mr Rennie had decided to seize the initiative and declared: "the time for action is now".

Mr Rennie, who unveiled his plan at an Edinburgh nursery this morning, said: "Liberal Democrats have an ambitious plan to get Scotland back on track by making the biggest investment in education since devolution with just one pence on income tax.

"A Scottish education was once the envy of the world. It has fallen hard and fast. But we have the plan that will put it right back up there.

"To get fit for the future our economy and our children need the best education. If we fail to act, a generation of children will miss out on the quality education they deserve. Every day counts. Kids cannot get their time at school back once it is gone."

The MSP insisted his proposals were progressive, with raised tax thresholds achieved during the 2010-15 coalition protecting those on low and middle incomes. Strategists said that 42 per cent of the £475m generated would come from the 12 per cent of richest individuals, with someone £100,000 paying 30 times as much as someone on £21,000. Those on the UK median wage would pay £2.90 a month more, according to the LibDems.

Mr Rennie added: "Our costed and progressive package of measures will ensure that Scotland races back up the international education standings to our world-beating best.

"We are protecting people on low and middle incomes thanks to the Liberal Democrats in government who raised tax thresholds to take thousands of people out of tax and cut it for thousands more.

"One penny is a small price for a big boost to get the country fit for the future. Our ambitious plan will enable every girl and boy in Scotland to make the best of themselves and get on in life. Progressives will support it, conservatives will oppose it. The question is where the Nationalists will stand. On investing in a first class future for our children, is Nicola Sturgeon progressive or conservative. I call on the SNP to back our plans in Scotland's interests."

Scottish Conservative chief whip John Lamont drew comparisons with the SNP's "penny for Scotland" policy, which it proposed at the Holyrood elections in 1999 but later ditched after it bombed with voters.

He added: “Not content with trying to win votes off the SNP by weakening their support for the union, now the Lib Dems are reduced to recycling discarded SNP policies.

"This announcement shows that Lib Dems have decided to join forces with a chaotic Labour party in lurching to the left on tax. They want to make Scotland the highest taxed part of the United Kingdom. It is unfair, utterly unnecessary and bad for Scotland.

“Working families who have had a difficult time over recent years need their pay-packets protected. At this election, that is exactly what the Scottish Conservatives will offer.”

A spokeswoman for education secretary Angela Constance said: "We are all committed to doing our best for our young people – but the Liberal Democrats’ sums simply don’t add up. And this SNP Government is already committed to investing significantly more than the £475 million Willie Rennie suggests these tax hikes will raise as part of our commitment to expand early learning and childcare.

"Willie Rennie wants to raise the Scottish Rate of Income Tax – but any increase would be unfair to the poorest taxpayers, who are already struggling because of the Tory austerity and cuts which his party enthusiastically backed.

"In contrast, this government has a fully costed and funded package of investment in education. Almost £5 billion is invested through local councils to deliver education each year, with our additional £100 million Attainment Scotland Fund now benefiting more than 300 primary schools that together support more than 54,000 pupils. Having invested £51 million specifically to maintain teacher numbers this year, we’ve committed £88 million to protect teacher numbers and places for new teachers across Scotland next year. Crucially, none of this involves or requires tax rises in the coming year. That’s what a credible government delivers for the people of Scotland."