UNIONS are pressing ahead with plans for the largest strike in decades as they appeared to reject the Coalition's "take it or leave it" deal on public sector pensions.

Ministers had appealed directly to workers not to walk out on November 30, describing the improved offer as the “chance of a lifetime”.

It included a pledge that anyone less than a decade from retirement would not have to pay a penny more.

But union leaders warned the concessions were not enough and that most employees would still have to work longer for less money.

Unison is today expected to unveil the results of a strike ballot of more than a million workers across the UK, including 150,000 in Scotland.

Others, including teaching and lecturing unions in Scotland, are due to follow suit in the coming weeks.

The pensions row triggered a walkout of more than 30,000 Scottish civil servants in June, but many more are expected to take part this time.

Finance Secretary John Swinney reiterated his call for the UK Government to change course, claiming that with the new deal, ministers had admitted their plans were “deficient”.

It came after Scottish ministers accused the UK Government of threatening them over the row.

The Coalition has said that if the reforms are not implemented in devolved schemes, including for teachers, then the Scottish Government will have to find the £100 million annual shortfall.

UK ministers insist that a rapidly ageing population means that public sector pension schemes are no longer affordable.

Danny Alexander, the LibDem Chief Secretary to the Treasury, announced the deal yesterday which includes an 8% increase on the previous offer, and a delay of seven years for full introduction of the reforms that would still see increased employee contributions.

If the revised deal was accepted, he added, no further changes would be made for 25 years. Ministers pointed out that under the latest proposals, a teacher earning £37,800 at retirement would receive £25,200 a year, up from the current £19,100. Mr Alexander hailed it as the “best we are going to get”.

“So I hope that the trade unions will now grasp the opportunity that this new offer represents,” he added.

“It is the chance of a lifetime to secure good, high-quality and fair public service pensions.”

But Tory colleague Francis Maude appeared to give the unions an ultimatum, describing the offer as conditional and saying that it was “as good as it’s going to get”.

Mark Serwotka, head of the PCS union, said: “Effectively, ministers are saying they will only raid pensions by slightly less than they were planning to.

“We will look at the details to see how they affect our members, but we continue our plans to make November 30 the biggest strike we have ever seen.”

Brendan Barber, the TUC general secretary, said the unions were still committed to preparing for strikes and the Coalition’s revised plans were not “judged as acceptable”.

Mr Alexander’s Labour shadow Rachel Reeves refused to condemn any potential strikes, saying: “I don’t think it is sensible to use megaphone diplomacy, to shout and tell one side or the other what to do.”

Simon Walker, director-general of the Institute of Directors, said the Coalition was repeating Labour’s errors.

Mr Walker added: “The public sector unions cannot be allowed to hold a gun to the Government’s head in this way.”

A number of teaching and lecturing unions in Scotland have balloted to strike, despite their pensions being devolved.

Mr Swinney said that his Government opposed plans to increase employee contributions.

He added: “The UK Government has made it crystal clear that if the Scottish Government does not implement the short-term increase in pension contributions, then it will reduce the amount of money in the Scottish Budget by over £100m in 2012/13 alone.

“This would have a knock-on effect on Scottish public services.

“The UK Government has today clearly accepted that its proposals for longer-term pension reform were deficient and needed to be revised.”