Identifying a failing primary school will earn some registered inspectors an extra Pounds 1,000.
The payment - on top of the basic fee of Pounds 5,000 plus expenses - is said to reflect the extra work generated once a school is deemed to require special measures.
But it was dubbed "naked bribery" this week by Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers. "This looks like an inducement to arrive at a certain decision," he said.
The cash is being offered by Taylor-Wallace Associates, run by Steve Taylor, a former head, and George Wallace, a registered inspector. Mr Taylor denied the Pounds 1,000 was a bonus paid for failing schools. "You can't fail a school to make money," he said.
He said that a failing school meant an extra six to eight days' work on top of the usual three to five days for a primary school. The average cost of inspection is Pounds 10,500.
Mr Taylor added: "We are not in the business of trying to fail schools. Most people would avoid those schools. They don't want to go near them because of the extra hassle. The stress factor for failing a school is fairly high - these people are teachers themselves passing negative judgments on colleagues. "
The revelation of the special payment plunges the Office for Standards in Education into fresh controversy over fees paid to "RgIs" because of the dearth of people willing to lead teams.
Earlier this month David Hart, general secretary of the National Association of Head Teachers, disclosed that RgIs earned more than Pounds 80,000 a year - three times as much as the average primary head. In April, The TES revealed that a Warwickshire agency was offering RgIs Pounds 54,000 plus substantial expenses to inspect 12 primaries.
OFSTED said the Pounds 1,000 payment sounded "quite a lot" but added: "It is a recognition that where a school is found to be failing more work is involved. "
It said on average RgIs conducted three primary inspections a year: some managed 17. Inspection contracts for the summer are up 35 per cent on the same period last year.
A three-day conference at New College, Oxford, next week, organised by the Office for Standards in Inspection, a group of academics and headteachers, will examine OFSTED's methods and value for money.