MPs have passed a controversial bill to exempt themselves from the Freedom of Information (FoI) Act .

The private members bill, introduced by Conservative MP David Maclean , exempts members of both the House of Commons and the House of Lords from having to release information under the Act, which came into force in 2005.

If passed, the bill will free MPs from having to release correspondence between themselves and their constituents, and will also remove the legal duty on public bodies to disclose any correspondence they receive from or send to MPs.

Supporters of Maclean’s Freedom of Information (Amendment) Bill claimed it would protect private letters that might contain sensitive information. But freedom of information campaigners said the law already protected such correspondence as confidential and argued that the move was designed to allow MPs to keep details of their expense claims secret.

The Mail on Sunday revealed last month that Maclean, the bill’s sponsor, had claimed £129,700 in expenses last year on top of his £59,000 salary, including £3,300 for a quadbike.

Despite previously being “talked out” of the Commons, the bill was reintroduced in May and passed by 96 votes to 25, with 25 Labour ministers v oting in its favour. Ministers who backed the bill included Trade Secretary Alistair Darling.

The bill could yet be defeated in the Lords when it goes for its second reading there on 21 June. Some peers have branded its FoI exclusions as “scandalous” and “hypocritical”.

In a small victory for FoI campaigners, their criticism prompted Maclean to draft an amendment to his bill to force MPs to reveal details about their expenses and allowances in an attempt to get it through the Lords.

But some peers have vowed to fight the amended bill, claiming it was “hypocritical” of parliament to exempt itself from any part of the Act.

Lib Dem justice spokesman Simon Hughes said: “We cannot ask every other public authority to be open to inquiry by law, but let parliament choose what facts and figures we reveal.”

In a separate development, the information commissioner Richard Thomas has reiterated that “vexatious” requests under the Act should be dealt with by greater use of existing provisions rather than new legislation.

His comments came as the government consults on proposals to restrict FoI further by including ministers’ and officials’ time in cost limits. Critics said this would make it easier to deny politically sensitive requests.

INFORMATION LEGACY

After 10 years of Tony Blair, the public mistrusts government information more than ever.

1997: Labour makes manifesto commitment to introduce a Freedom of Information Act. After its election, Blair government publishes Your Right to Know white paper.

November 2000: Freedom of Information Act passed, with five-year implementation delay.

1 January 2005: Act comes into force, placing duty of openness on all public bodies.

November 2006: Government proposes to tighten FoI on gr ounds of cost.

18 December 2006: David Maclean MP tables bill to restrict FoI bill.

18 May 2007: Commons passes second reading of bill, which now goes to Lords for approval.