The leader of the largest public sector union promises to mount the most sustained campaign of industrial action the country has seen since the general strike of 1926, vowing not to back down until the government has dropped its controversial pension changes.

Dave Prentis, general secretary of Unison – which has 1.4 million members employed by the state – described plans for waves of strike action, with public services shut down on a daily basis, rolling from one region to the next and from sector to sector.

He said there was growing anger over a public sector pay freeze that could trigger more disputes further down the line and that the changes would unfairly penalise women, who form the majority of low-paid public sector workers. "It will be the biggest since the general strike. It won't be the miners' strike. We are going to win."

In an interview with the Guardian, Prentis – who also chairs the public sector group at the TUC – repeatedly insisted that he still hopes to negotiate a settlement with the government through talks that are currently under way.

But the prospect of a resolution looks increasingly remote after the government unilaterally set out details of the new public sector pension scheme on Friday, pre-empting the conclusion of the talks. Brendan Barber, the general secretary of the TUC, called the move "deeply inflammatory".

Prentis said: "I strongly believe that one day of industrial action will not change anyone's mind in government. We want to move towards a settlement. The purpose of industrial action is not industrial action, it is to get an agreement that is acceptable and long-lasting. But we are prepared for rolling action over an indefinite period. This coalition has got to open its eyes and see that in just reacting to a Daily Mail view of the public sector they are walking into a trap of their own making."

Prentis also called on the Labour party to support the unions' battle against the pension changes, saying that remaining silent will "become an issue".

The government has confirmed that it will raise pension contributions by 3.2 percentage points, increase the retirement age to 66 and move to a career average scheme to replace the more generous final salary version. Ministers argue it is unfair for other taxpayers to pay for more generous schemes for public employees than they might get in the private sector.

The unions say it amounts to an additional tax on public sector workers, with their additional contributions – a de facto pay cut – being used to reduce the deficit rather than fund pensions. It comes on top of job cuts, a pay freeze and controversial plans such as those for the NHS.

Prentis said that while pensions were the focus of the unions' industrial dispute – and the only issue that they could legally jointly strike on – his members were equally angry about the coalition's deficit reduction programme and its effects on the public sector.

"You can't just look at what's happening around pensions as a single issue. All our members provide public services. You look at what this coalition has decided to do to reduce the deficit and it's decided that most of the deficit reduction programme will be at the expense of our public services," he said.

"The people that we represent are facing redundancy, a two-year pay freeze, while inflation is 5% and gas prices are going up 20%, and they are desperately worried about privatisation of the services they have committed their working lives to."

He accused the government of trying to "soften up" public sector workers' rights to pave the way to privatising elements of the state. Referring to a consultation that could remove state employees' rights to keep their public sector pensions if their service is outsourced to the private sector, he said: "It means that cowboys that we used to have in the 1980s can put in bids that will always undermine the public service bid and they will get the contract not on the quality of work but because they are cheapest. It's just to soften the way for privatisation."

Turning to Labour, to which Unison is affiliated – individual members have an opt-out – he said: "We want our Labour party to be the voice of opposition. We're worried that some of the senior people in the party still have to make statements as if they are in power, not opposition."

Prentis added: "I've got a lot of time for Ed Miliband. He's new, he's only been there for eight months and he will improve – and we've got to give him time to do that – but the way in which certain elements in the party are not uniting where we need them to be is not helping. If the Labour party stays quiet that will be an issue. This isn't a kneejerk reaction, this will be a long programme of action and we will expect the Labour party to support that."

Unison is one of Labour's largest donors, giving £423,000 in the past year alone.

Prentis said he had full support from his members and they were now recruiting support for the campaign outside the workplace, sending representatives into community groups to garner support. A motion at the union's conference next week would formalise this campaign, recognising that traditional workplace union recruitment is falling.

Angela Eagle, Labour's shadow chief secretary to the Treasury, said: "What we are seeing today is the latest calamitous episode of this government's completely chaotic way of running the country.

"Today, Danny Alexander [the Treasury chief secretary] has made an announcement about the retirement age whilst they are in the middle of negotiations with the trade unions. If they are serious about reforming public sector pensions and serious about getting this proposal agreed then Danny Alexander has gone about it in the most incompetent way imaginable."

She added: "Strikes are always a failure on both sides. Everyone agrees public sector pensions need to change as people live longer. But the government should be getting round the table and talking changes through. Instead we have got another bout of mismanagement and chaos."