It is being billed as the battle of the ex-chief inspectors. The two men who once sat in judgement on the nation’s schools are now rivals in a battle to become the biggest players in the private education market.

It is an open secret that no love was lost between them when they were colleagues at the Office for Standards in Education. And the sniping continued as Chris Woodhead relinquished the top slot to his deputy Mike Tomlinson.

Mr Woodhead then began to dabble in journalism and is now professor of education at the private Buckingham university.

He also chairs Cognita, a company which announced the purchase last week of 17 schools from Asquith Court, the nursery care provider, for pound;60 million. This followed the earlier acquisition of Quinton House school in Northamptonshire.

With prep schools at the heart of the company’s expansion plans, Cognita is in direct competition with Global Education Management Systems (Gems), whose advisory group is chaired by Mr Tomlinson.

Since leaving Ofsted Mr Tomlinson has headed the inquiry into secondary education and is chair of the Hackney Learning Trust, which runs education in the east London borough.

Gems already has 13 private schools in the UK, most of them prep schools, and has a pound;190m war chest to expand its own empire.

The rivalry between the two has been stoked by the recruitment of at least two Gems employees by Cognita.

Critics fear the competition could lead to a drop in standards as private companies attempt to undermine each other by cutting corners.

Mr Woodhead, who resigned as the chief inspector in 2000, admitted fees could fall as more companies embark on mass ownership of schools, but denied standards would be affected.

“In principle, competition between and among schools is a good thing,” he said. “Competition in other areas of human activity has often led to a rise in standards while prices have been driven down.”

And for once Mr Tomlinson agreed: “Competition will be good for the independent sector. As with the maintained sector, it thrives on competition however you define it.”

He dismissed fears that increased interest in the private sector reflected a decline in standards at state schools.

“The maintained sector is improving quite considerably - there are many, many good schools,” he said.

“All this means is more choice. We all want every child to have the best possible education that can be provided in the independent or maintained sector.”

Last month Gems, backed by the Dubai millionaire Sunny Varkey, ventured into the state sector for the first time by purchasing 3E’s, a non-profit-making company set up to manage failing schools. But Mr Woodhead ruled out any similar plans for Cognita.

WOODHEAD v TOMLINSON

Round one: Tomlinson becomes director of inspection in 1995 leading to tensions at the Office for Standards in Education as the pair disagree on how it should evolve.

Round two: Tomlinson replaces Woodhead as chief inspector of schools in 2000, signalling an instant change in direction for Ofsted as the latter’s authoritarian, top-down, critical style is abandoned.

Round three: Woodhead criticises Ofsted’s new more conciliatory approach in his 2002 book, Class War, branding Mr Tomlinson’s calls for a more “responsive” inspection system as “weasel words”.

Round four: Woodhead brands Tomlinson’s 14-19 reform plans a “disaster”.

Round five: The pair go head to head in the private schools market but at least they agree on one thing - increased competition in the independent private sector will only benefit pupils and parents.