Scottish LibDem leader Tavish Scott proposed the pay cut – intended to help balance the budget during a tight squeeze on public finances – as part of a package of measures that would ensure his party’s support for the minority SNP Government’s budget, which has to be passed by parliament in the New Year.

Using data obtained through freedom of information requests, the LibDems have calculated that the bill for senior Scottish public sector workers taking home more than £80,000 per year

is £600m.

A 5% pay cut for the ­highest-paid staff in health boards, councils, universities, government agencies and quangos would save £30m, the party estimates.

Mr Scott said he wanted to see the Government look at this kind of top-slicing ­proposal to make sure people on the bottom of the public-sector pay grade are protected from cuts.

“We’re asking the Government to look at the overall public-sector pay bill in Scotland and take out 5% across that pay bill at the very top, in other words, on people earning more than £100,000, so that we can protect people at the bottom and also help with the overall pressure the finances of the public sector are under.”

Yesterday Mr Swinney said he was “considering” the matter that had been raised in budget talks with LibDem negotiator Jeremy Purvis.

Neither party would discuss details of other measures that they are discussing.

Mr Scott said there were 1200 people in the NHS alone earning more than £100,000 and his proposals would go even further than in England and Wales, which will see a 1% cap on pay rises for public-sector workers.

Mr Swinney said Scottish Ministers have already set an example by taking a pay freeze, which will also apply to senior civil servants, and the Cabinet has already agreed to extend that approach to the highest paid people across the public sector who come under the government’s remit.

“I will be reporting back to Cabinet, and further announcements will follow in due course,” said Mr Swinney.

“LibDem Westminster policy actually advocates a pay freeze for all employees in the public sector – including nurses and others – whereas we believe in protecting the position of the low paid.

“It is the highest paid who must shoulder the biggest burden.”

Scottish Labour’s Shadow Finance Secretary Andy Kerr cast doubt on how the LibDem plan would be imposed on senior public-sector workers in practice.

He maintained that measures to stimulate the economy were what his party would be demanding from the

budget. “We certainly also called for a pay freeze on the highest earners, but I’m not sure that’s the top of my list of priorities,” said Mr Kerr.

Labour is still furious over the cancellation of the Glasgow Airport Rail Link and will campaign for the £182bn project to be reinstated.

Ministers cancelled the airport rail link citing Westminster-imposed cuts to its budget, but Labour insist the level of cash is actually rising while the SNP maintain there will be £814m less to spend.

“A primary school pupil can tell Mr Salmond he’s got his sums wrong over the budget,” said Mr Kerr.

“The facts speak for themselves as official Scottish government figures show the budget for 2010-11 is £35.49bn. The 2009-10 budget is £34.57bn. That is almost £1bn more, and Scotland’s biggest ever budget.

“I’ll even lend Alex Salmond my calculator if he cannot do the arithmetic. But the SNP think if they repeat a lie often enough people will believe them.”