Ofsted has been accused of giving academies special treatment after documents revealed that inspectors have liaised with the Government about the timing of inspections.
It also emerged that Ofsted has been given the chance to shape academies policy - a move that anti-academy campaigners claim is a conflict of interests, as the inspectorate's task is to pass judgment on all schools without favouring one type over another.
Documents passed to The TES show that Her Majesty's Inspectors have discussed with civil servants the "optimum timing" for inspections of new academies.
These inspections are designed to be "helpful in promoting the academy's progress", according to the documents.
Roger Titcombe, a former head and a member of the Anti-Academies Alliance, said: "This raises questions about the independence of Ofsted from the Government.
"Ofsted seems to have taken a stake in the success of the academies programme. That's bound to raise questions about objectivity and conflicts of interest in monitoring the standards of academies."
However, there is no concrete evidence of inspectors favouring academies in individual reports. For example, since 2005 Ofsted has declared two academies to be seriously underperforming.
The accusations against Ofsted arise from documents obtained by Mr Titcombe through Freedom of Information requests.
The documents show that in December 2004 the academies division of the then Department for Education and Skills (DfES) drew up a "protocol" with Ofsted for "working with academies".
Under the heading "Ofsted involvement in the academies policy", the division says it will seek advice from Ofsted on initial proposals to create an academy.
It adds: "Academies division will keep Ofsted informed of progress, and provide Ofsted with the opportunity to contribute to the development of the academies policy, through termly meetings."
The protocol shows that Ofsted was asked to keep the division informed of its monitoring of all low-achieving secondary schools, those in special measures and "any other Ofsted visits to schools".
It adds that: "Ofsted and academies division will consider the optimum timing for HMI to make a monitoring visit to a newly opened academy.
"An initial monitoring visit may be made as early as the second term if Ofsted or academies division (AD) have serious concerns about the academy's progress or if Ofsted and AD agree that such a visit will be helpful in promoting the academy's progress."
The protocol adds that the first inspection of a newly opened academy will be led by an HMI, the most senior level of inspector. But inspections of other schools do not have to be led by HMI.
It also says: "The above procedure has been agreed between the DfES and Ofsted to acknowledge and accommodate the new and different nature of academies."
Notes of a meeting on October 4, 2006, between HMI and department officials appear to show positive academy inspections being greeted favourably: "(Name blanked out) gave general feedback including progress made and information on positive inspections. All pleased with (school name blanked out) and (school name blanked out) reports."
An Ofsted spokeswoman said that the inspectorate's monitoring visits to academies shortly after they opened should not be confused with routine inspections, which it carried out at academies in the same way as at other schools.
Ofsted and the Government this year updated their academies protocol, with the phrase about giving the inspectorate the chance to "contribute to the development of academies policy" watered down to a stipulation that Ofsted and the academies group will "exchange relevant information on policy and developments at termly meetings".