But a Committee on Parliamentary Privilege in the 60s urged MPs to be extremely careful about exercising such powers.

BBC: How can select committees avoid being misled?

The Joint Committee on Parliamentary Privilege (at 5.05pm) is looking into some of the tangled issues around the powers of parliament and the legal protections MPs have in order to represent their constituents.

BBC: Week ahead in committees

And the two high priests of Parliament, Sir Robert Rogers, the Clerk of the Commons, and his Lords opposite number, David Beamish, Clerk of the Parliaments, stage a joint appearance before the Joint Committee on Parliamentary Privilege.

BBC: Week ahead in committees

Jill Pay was giving evidence on 7 December 2009 to the specially convened Committee on Issue of Privilege, set up following the search of Mr Green's offices.

BBC: Committee on Issue of Privilege

"Denis MacShane's letter to the committee cannot be disclosed under parliamentary privilege" he said.

BBC: No privilege for disgraced former MP Denis MacShane

She said she will do nothing except render privilege speeches, and not be a member of any committee.

CNN: Philippine Contenders

We will not assert the privilege in court without first following our own formal process, including review by a Justice Department committee and the personal approval of the Attorney General.

WHITEHOUSE: President Obama: Our Security, Our Values