By Sean Coughlan
BBC News education reporter
The truancy rate is higher now than in 1997
The truancy rate in schools in England has reached its highest ever level, according to the latest figures.
The truancy statistics for the first two terms of the last school year show 1.03% of school sessions were missed without permission, up from 0.97%.
When Labour entered office in 1997, the annual rate of unauthorised absence was 0.7% - a constant figure since 1994.
"Missing school for no good reason is totally unacceptable," Schools Minister Vernon Coaker commented.
These latest figures - covering the autumn and spring terms of 2008-2009 - show the rate of unauthorised absences as running higher than any annual figure since 1994, when figures were first published.
A spokeswoman for the Department for Children, Schools and Families says the increase in unauthorised absences reflects a tougher line from schools in turning down parents' requests for time off for their children.
"The rise in unauthorised absence is not what we want to see, but as schools are cracking down on absence it's inevitable that they will be stricter about authorising it - meaning that unauthorised absence will rise," said the DCSF spokeswoman.
The number of persistent truants - missing at least one day a week - has fallen from 273,000 to 241,000 pupils.
The way of releasing truancy figures has changed - with these latest figures representing the worst figures under this new measurement.
But looking back further, the figure of 1.03% for half days missed without permission is higher than any of the last 15 years.
Between 1994-1995 and 1999-2000, the rate for unauthorised absences remained at 0.7% - rising steadily to 0.79% in 2006, after which measurement switched to a termly basis.
The government made a priority of tackling truancy, setting a target of reducing it by a third in 1998.
There were high-profile crackdowns - with the National Audit Office saying in 2005 that £885m had been spent on tackling truancy without reducing the rate of unauthorised absences.
There were 10,000 prosecutions of truants' parents in 2007 in England - and up to 2007, 133 parents had been sentenced to imprisonment.
But the figures for missing lessons without permission remains higher than a decade ago.
These latest two-term figures show another failure to cut the truancy rate.
The number of absences with permission has fallen - but the overall rate of absence rose from 6.26% to 6.31%.
Illness remains the single most common reason why pupils are not in school - 59% of the total.
But the second most frequent reason was pupils taking a family holiday - both those agreed with the school and those taken without permission or those in which pupils do not come back at the agreed time.
Persistent truants - defined as pupils who miss more than a fifth of school sessions - accounted for 46% of unauthorised absences.
There have been particular efforts to reduce truancy among this group and the figures show that the number of persistent truants in secondary school has fallen from 209,000 to 169,000 - from 6.9% to 5.7%.
And the DCSF spokeswoman said that the level of persistent truancy was a more relevant measure than the headline figure for unauthorised absences.
"Persistent absence can have a negative impact on young people's life chances, so it's encouraging to see that our targeting of this group is working and the number of persistent absentees is falling," said Schools Minister Vernon Coaker.
Shadow Schools Minister, Nick Gibb, said: "The increase in the number of children skipping school is very worrying. Children need to be in the classroom if they are to get the education they need to succeed later on.
"The government's multi-million pound truancy strategy has failed. It's time to get to the roots of the problem, which are low levels of achievement and poor behaviour."
Head teachers' leader, John Dunford, backed the argument that unauthorised absences would be inflated by schools refusing to give permission for term-time holidays.
"Schools work extremely hard to raise attendance and get persistent truants back into school. This can only be successful if parents co-operate with the school and ensure that their child is there every day," said the ASCL general secretary.
"A rise in unauthorised absence is more likely to occur because schools have tightened up on the definition of 'unauthorised' than because of a growth in truancy. In particular, schools have become stricter over parents taking their children out of school for holidays in term time," said Dr Dunford.