"I thought the controls would be tougher," says reporter Karl Mercer

"We made up two names but put down the real telephone numbers of people on the team, but we received no check calls," Karl Mercer said.

He did not use his own name but gave the name of someone who had qualified as a teacher - and faxed the agency that man's qualifications.

The team made up the names of the "referees", who they said had been the head teachers of two London schools, which have since closed down.

The reporter said the agency offered him work at a primary school in Romford for two days last week.

The agency is investigating the claims.

In a statement, Teaching Personnel of Welwyn Garden City said: "We carry out checks and ask for references which are normally checked.

"We take the matter very seriously."

We even suspected that a couple of them were operating out of literally a Ford Cortina with a mobile phone - and couldn't possibly be doing the sort of checks that we would want them to

Chris Williams, Newham Council

The issue of checks on supply teachers is one which concerns schools, parents and councils alike.

Chris Williams, the director of the teaching department at Newham Council said: "We were concerned that some of these agencies didn't have good practice.

"In fact we even suspected that a couple of them were operating out of literally a Ford Cortina with a mobile phone - and couldn't possibly be doing the sort of checks that we would want them to."

With schools relying more and more on supply teachers, the government plans to bring in a voluntary system to regulate supply teacher agencies.

The number of temporary or supply teachers - on contracts of a month or less - has gone up from 12,200 in 1995 to 19,000, according to official statistics.

Quality marks

The government is to introduce a system of quality marks or stars, to show that a recruitment agency has met certain standards.

The details are still being worked out but it is thought agencies would be assessed on recruitment - how well they check references and select staff.

The checks might also take into account the treatment of recruits - how well they are looked after in terms of training and development - and the standard of service the agencies give to schools.