Truancy in England's secondary schools is at least 18% higher than thought.
A third of pupils missed at least one school session without permission
Collecting the figures termly rather than annually has shown a slightly higher rate of authorised absences, and much higher unauthorised, in 2005-06.
Children from poor families were almost three times more likely to play truant than their fellow pupils.
The government says a small percentage of pupils accounted for more than half the absences, and targeted intervention can bring "spectacular" improvements.
The statistics released by the Department for Education and Skills relate to the half-day sessions during which pupils registered in schools should have been there.
The new method of counting means schools report what happened in the previous term, rather than just making one annual return.
Even so, the summer term is still only counted up to the spring bank holiday weekend at the end of May, so the true picture is likely to be even worse.
The new figures show that authorised absences accounted for 6.82% of half-day sessions, which was 0.08 percentage points higher than under the old system.
Unauthorised absences were 1.42%, up 0.22 points.
Overall absences totalled 8.24%, up 0.3 percentage points.
Girls were a little more likely than boys to have had authorised absences.
The biggest jumps between the old and new figures were in academies and city technology colleges, where unauthorised absences were shown to be 26.7% and 29.6% higher - compared with the overall 18.3% difference.
The government highlighted the fact that just 2.4% of those enrolled in schools accounted for more than half the total number of sessions missed without permission.
There were 217,300 "persistent absentees" - defined as those who were away for more than 63 sessions in total, or about a fifth of the school year.
Academies had the highest proportion of these, at 9% of those enrolled compared with 7% overall.
Persistent absenteeism among pupils from minority ethnic backgrounds in general was "significantly below" the rate for white British pupils, officials said.
Schools Minister Jim Knight said the figures showed a small minority of persistent absentees accounted for most absence.
"It makes sense to clamp down on these as an absolute priority.
"Working with schools which we know had significant numbers of such pupils has helped them achieve spectacular results in improving attendance records," he said.
"For example, 27% fewer truants in the 198 schools we supported last year, and this year 20% fewer persistent absentees compared to last spring."
However, another big rise shown in the new figures is in the number of pupils who were absent at some point without permission.
This had been recorded as 794,877 or 26.5% of the total, and is now shown as 973,980 or almost a third (32%).
The department's statisticians said the new data provided a more precise basis of measurement but there were some quality concerns.
For example, reasons for absence might not have been received before the census returns were submitted, and if pupils changed school they would be counted more than once.
Opposition politicians said the new figures highlighted the government's failure to tackle truancy.
Shadow schools minister Nick Gibb said the billions of pounds spent on various anti-truancy initiatives had clearly failed.
"The focus of the government must be on behaviour and discipline in our schools, so they are safe and secure places where learning and academic rigour can prevail."
Liberal Democrat education spokeswoman Sarah Teather said: ¿The sad fact is that one in three children who truant do so because they are being bullied.
"If we had a little more joined-up thinking from ministers to tackle bullying more children would get a full education."