THE SNP will back the introduction of a 50p top rate of income tax across the UK, senior Nationalists have announced, in a move that piles further pressure on Labour leader Ed Miliband to agree a possible deal with the party after the election.

After days of hints and speculation, the move was confirmed by Deputy First Minister John Swinney and SNP deputy leader Stewart Hosie on the closing day of the SNP conference in Glasgow.

The top rate of income tax, paid by those earning over £150,000, was raised to 50p in the final days of the last Labour government but cut to 45p by Chancellor George Osborne in 2013.

Restoring the 50p rate is one of Labour leader Ed Miliband's key election pledges.

The SNP's decision to match the policy comes as the party leadership is talking up its chances of an informal deal with a minority Labour government after the next election.

On Saturday, Nicola Sturgeon reached out centre-left voters south of the Border, promising to pursue progressive policies for the whole UK, in a bid to make it harder for Mr Miliband to turn his back on the Nationalists.

In a BBC interview earlier in the day Mr Hosie said the SNP should have a say in a minority Labour government's first Queen's speech, even if they only offered support on a vote by vote basis.

He said: "If Ed Miliband is seriously saying he could run a minority government without speaking to the SNP, if the polls are to be believed, that is a very dangerous tactic for him to take.

"It would be high handed and arrogant for there not to be negotiations [between Labour and the SNP

Scottish Labour last night insisted the SNP's position was "confused".

In his conference address, Mr Hosie, who is also SNP's Treasury spokesman, said the SNP would "absolutely" support the reintroduction of the higher rate.

He told the conference: "Labour talk about re-distribution and a 50p rate of tax.

"This party moved the vote against the tax cut for millionaires. Everyone of our MPs has already voted against a tax cut for millionaires when it counted.

"For all their talk the Labour Party did not. So let there be absolutely no doubt.

"We would not have cut the 50p tax rate for the very highest earners during a recession.

"We still think it is right that those with the very broadest shoulders should bear a little more of the burden.

"So in the next Parliament, SNP MPs will support the re-introduction of the 50p rate of tax."

Earlier, Mr Swinney said the SNP would back a 50p tax rate as part of a wider commitment to reducing inequalities.

"Fairness extends to taxation," he told delegates.

Mr Hosie said he hoped there would be a "huge group" of SNP MPs in the Commons after May 7, adding that they could "hold the balance of power" in a hung parliament.

He said they would vote to abolish the so-called Bedroom Tax and to scrap zero hours contracts, two other Labour pledges.

He also repeated Ms Sturgeon's promise to push for a national minimum wage of £8.70 by the end of 2020, 70p more than Labour's plan.

Scottish Labour's finance spokeswoman Jackie Baillie claimed their backing for a 50p tax rate "exposes the confusion at the heart of the SNP"

She added: "Last Sunday, the former First Minister confidently asserted there would be no new taxes.

"Today, John Swinney declares his belated support for one of Labour's progressive taxes.

"Who are voters to believe? Mr Swinney, or Mr Salmond?

Scottish Conservative enterprise spokesman Murdo Fraser said: "This is an anti-business move which would harm job and wealth creation in Scotland.

"It has been shown that when the upper tax tate is cut, collection actually increases.

"This is more evidence that both the SNP and Labour are determined to drag Scotland dangerously to the left."