Ed Miliband has repeated his refusal to condemn strike action by up to two million public sector workers on Wednesday, 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.
"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 on Monday that union leaders wanted to "wreck" economic recovery and cause public misery.
More than 1,000 demonstrations will be held across the UK on Wednesday 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."
But unions said many workers involved in Wednesday'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 on Monday 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.
Christine Blower, general secretary of the National Union 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. 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."