The information watchdog has established an expert team to decide whether advice to the Prime Minister on the legality of invading Iraq should be made public. The unit will have access to top-secret legal opinion as well as correspondence between Lord Goldsmith, the Attorney General, and Tony Blair.

The information watchdog has established an expert team to decide whether advice to the Prime Minister on the legality of invading Iraq should be made public. The unit will have access to top-secret legal opinion as well as correspondence between Lord Goldsmith, the Attorney General, and Tony Blair.

The Information Commissioner, Richard Thomas, has had several complaints under the Freedom of Information Act about the Government's decision to withhold the advice.

His decision to appoint a special team comes amid growing frustration with the Government's refusal to release files under the Act. The Independent, among others refused permission to see the advice, has learnt that the unit has been established because of "the unusual circumstances".

Under the Act, Mr Thomas has the right to demand the Government release the file if he decides it is in the public interest. His decision is being regarded as a test case. The watchdog's lawyers are expected to examine the Government's contention that legal opinions formed by the Attorney General are never released.

The investigation will start in a fortnight, when "we have received all the related complaints and are able to decide what documents in addition to the advice itself the commissioner may wish to inspect".

Sir Menzies Campbell MP, deputy leader of the Liberal Democrats and a senior barrister, said the Government "has set its own precedent" when it decided to publish part of it. "To understand the full measure of the advice we need to see the opinion in its entirety," he said. "The argument against the release of advice is that it is against the public interest but this is a case where public interest points in the opposite direction."

The commissioner has also had complaints that the Government has breached the terms of the Act by failing to contact people who have requested information before releasing a response publicly.

David Lowry, an environmental research consultant, complained to the commissioner after he found the refusal to release the legal advice on a government website. By law, the Government must issue a refusal notice directly to him.

The Information Commissioner wrote to Mr Lowry after he complained, saying he will raise the matter "at the conclusion of our consideration of the other complaints".