The call from the Liberal Democrats comes as headteachers said the annual cost to some schools of employing an agency teacher was now pound;5,000 more than for a young permanent member of staff.
David Hart, general secretary of the National Association of Head Teachers, claimed that prices for supply teachers overall have risen by up to 50 per cent in the past year. This has taken place against a backdrop of a serious national shortage of temporary staff.
Phil Willis, Lib Dem education spokesman, has called on OFTofficials to investigate whether the "limited" number of recruitment agencies means cartels operate in the sector.
In a letter he also calls on the watchdog to look into whether the profits made by agencies are "excessive". Officials have promised to meet him to discuss his concerns.