Since February 2007, 12 MPs have travelled overseas with the British Council to destinations including Thailand, India and Malawi, often at a cost of thousands of pounds.

MPs must normally declare any hospitality they receive from outside organisations, and the British Council does not appear on a list of bodies whose gifts are exempt from the requirement.

When The Sunday Telegraph used the Freedom of Information Act to ask the Commons authorities why the trips were not being declared, Mr Martin stepped in and took the highly unusual step of signing a special certificate preventing the release of any information about how the decision was reached.

The document, headed ‘The Certificate’, cites Parliamentary privilege as the reason to impose secrecy. It even halts any further investigation by Richard Thomas, the Information Commissioner, who would normally have the power to intervene.

The Speaker’s move to block information that campaigners claim should be in the public domain has been condemned by MPs as well as civil liberty advocates.

In recent months, Mr Martin has been heavily criticised for trying to suppress details about MPs’ expenses and for trying to exempt aspects of their work from the Freedom of Information Act.

It is also not the first time that he has used the controversial certificate. In 2006, Mr Martin issued a certificate banning the release of a list of MPs’ staff under Freedom of Information laws.

Trying to get details of MPs expenses out of the Commons’ authorities has been like trying to get blood from stone. It is a direct contrast to the opennesss and transparency of the National Assembly for Wales.

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