Mr Sinnott's death from a suspected heart attack came just weeks before he was due to lead the first national teachers' strike for 21 years in a dispute over pay. Union colleagues and political opponents put aside their differences to remember a passionate campaigner for education.

Prime Minister Gordon Brown was among the first to pay tribute. He said: "Steve Sinnott was inspirational in his devotion to teaching, not just for children in Britain, but around the world. His commitment to teachers and education will be remembered."

Devastated NUT officials described Mr Sinnott as "the most compassionate of men".

The union pledged to go ahead with the one-day strike over pay on April 24 as the best way to show respect for its former leader.

In a statement, the NUT said: "The loss of Steve Sinnott is grievous for the teaching profession, catastrophic for all NUT members, and desperately sad for his colleagues and friends."

Christine Blower, who becomes the NUT's acting general secretary, added: "I know that he would have wanted the union to go ahead with all its campaigns because he believed in all of them with his heart as well as his head. The best way to mark our respect would be to maximise the effect of the campaigns to which he was so committed."

Mr Sinnott was said to have been in a "buoyant" mood about the strike in recent days, enjoying the strong support for the action that he was receiving from colleagues.

Schools Secretary Ed Balls, with whom Mr Sinnott clashed over the pay campaign, said he was "deeply shocked and saddened" at the news.

"Our thoughts are with Steve's family and friends at this very difficult time," he said. "Steve was a passionate advocate for teachers and a great believer in the power of education to transform the life chances of children and young people. He will be sadly missed."