The latest figures show that 1,264,103 primary and secondary pupils took unauthorised absence from school in 2003-4. This is a rise of 24 per cent since Labour was elected in 1997, when 1,029,448 pupils played truant.
Labour has a long-standing pledge to reduce school truancy, introducing a range of measures such as local-authority truancy sweeps, and fines for parents of persistent truants.
But Tim Collins, Conservative education spokesman, said that the figures proved the measures had been ineffective. He said: "Labour promised to cut truancy by a third. Instead it's up by a third. After countless initiatives and millions of pounds spent, ministers have nothing to show for all their talk."
Truancy is measured by the percentage of half-days missed through unauthorised absence. Figures reveal that 1.14 per cent of half-days were missed in secondaries, and 0.14 per cent in primaries, in 20034. There has been little change since 19978.
The Department for Education and Skills said that although the number of truants was increasing, they were tending to miss fewer sessions.
The department insists that a hardcore 2 per cent of pupils are responsible for nearly half the unauthorised absence in schools.
A spokesman said: "School attendance is now at record levels, with 17,000 more pupils regularly attending school every day in the last year, 40,000 more than in 1996-7.
"We are continuing to bear down on the hardcore of serial truants, through a combination of robust support for parents who face genuine difficulties in getting their children to attend school, and tough sanctions for those who simply refuse to do so."
Steve Sinnott, general secretary of the National Union of Teachers, has said: "Teachers and the Government have put a lot of effort into combating truancy. Clearly something more needs to be done. But imposing fines on parents is not the way forward. It's a more complex problem than that."
Meanwhile, the school with the worst truancy record in the country has announced that it is to close in the summer. Last year, 12.7 per cent of half-days at East Brighton College of media arts were lost to truancy.
But Mark Whitby, the headteacher, said that this was a significant improvement on the previous year's figure of 20 per cent.