Ed Miliband has repeated his refusal to condemn strike action by up to two million public sector workers tomorrow despite describing their action as causing "terrible" disruption.
The Labour leader said he "hated" the effects of the strike, including closed schools and cancelled operations, but would not condemn the action.
Referring to a headteacher he had seen on ITV Daybreak, Mr Miliband said: "He and many of his colleagues feel that they have been put in an impossible position by the Government because the Government has stopped negotiating over these public sector pensions.
"They are imposing - and I don't think most people recognise this yet - a 3% tax rise on some of the lowest paid workers in the country, not actually to help them with their pension but to help pay off the deficit.
"Of course we have to pay off the deficit but to target public sector workers in the way that they have been doing is not fair.
"So the disruption is terrible but I am not going to condemn those who have taken this decision."
Mr Miliband's remarks to ITV Daybreak come after Education Secretary Michael Gove claimed yesterday that union leaders wanted to "wreck" economic recovery and cause public misery.
More than 1,000 demonstrations will be held across the UK tomorrow as part of the action, which Mr Gove said would lead to the closure of nine out of 10 schools in England.
In an outspoken intervention in the bitter dispute, Mr Gove said it was "unfair and unrealistic" to expect taxpayers to foot the increasing bill for pensions.
"Among those union leaders are people who fight hard for their members and whom I respect," he said.
"But there are also hard-liners - militants itching for a fight.
"They want families to be inconvenienced.
"They want mothers to give up a day's work, or pay for expensive childcare, because schools will be closed.
"They want teachers and other public sector workers to lose a day's pay in the run-up to Christmas.
"They want scenes of industrial strife on our TV screens, they want to make economic recovery harder, they want to provide a platform for confrontation just when we all need to pull together."
But unions said many workers involved in tomorrow's walkout would be taking strike action for the first time in their lives, adding that the Government was becoming "desperate" because it was losing public support.
Unison leader Dave Prentis said yesterday that there was "absolutely no chance" of reaching a deal in the next few days over the Government's controversial pension reforms, announcing that the union had doubled its recruitment in recent weeks as a result of the dispute.
"It could be the biggest action since the 1926 General Strike," he predicted.
Christine Blower, general secretary of the National of Teachers (NUT), said: "This dispute has been created by a Government which is determined to steamroller through pension reform that will irreparably damage teachers' pensions.
"The issue has united the teaching profession, as will be demonstrated on November 30.
"This strike has nothing to with 'militants' but everything to do with teachers and headteachers who do not believe the Government is being fair or reasonable."
Unison said tomorrow would be a "women's day of action" because of the huge numbers of women taking part.
Mr Prentis said he did not trust the Government's figures on pensions, adding that opinion polls showed the public believed unions more than ministers, and had sympathy with public sector workers.
"The public believes in the justice of our case despite the best efforts of the coalition to denigrate union leaders and public service workers."
Mr Prentis said it was "incredible" that huge bonuses will be paid in the City this Christmas given the state of the economy and the Government's "attack" on public sector pensions.
Unison said applications to join the union had increased by 126% since its strike ballot result was announced earlier this month, with 81% from women.