Mr Lewis said most of the persistent truanting he had experienced was parentally condoned.

"We need to increase the instruments that are available so that we can deal with parents who collude in persistent truanting," a spokesman for Prime Minister Tony Blair said.

Some 315 of the 461 had an identified reason for such regular absenteeism, such as a medical illness, a bout of ill-health or persistent truanting, and three of the 315 had already been diagnosed as having CFS.