Attorney General Lord Goldsmith is being questioned by the Constitutional Affairs select committee over his constitutional role.
Lord Goldsmith's role has become increasingly controversial as different political pressures have mounted on the Government.
The recent decision to abandon the Serious Fraud Office investigation into corruption involving the Al-Yamamah arms deal with Saudi Arabia has attracted heavy criticism.
Lord Goldsmith recently told the Lords that the decision had to be taken by the Serious Fraud Office director.
He also informed peers that the decision on the BAE deal had been a "specific instance", with the Saudi authorities threatening to withdraw intelligence co-operation if the investigation went ahead
Cash for honours
The most dangerous issue to the Government is the role of the Attorney General in deciding if people charged under the 'Cash for honours' scandal should be prosecuted.
Lord Goldsmith would have the right to rule whether or not a prosecution would be in the public interest.
He said he had no intention of "standing aside" from the probe and that all decisions would be taken "impartially and objectively".
As head of the Crown Prosecution Service, the Attorney General is usually consulted on difficult or high-profile prosecutions.
The Director of Public Prosecutions (DPP) Ken Macdonald has already stepped aside because he is a former colleague of Cherie Blair, while Met Police chief, Sir Ian Blair, who has worked closely with the PM for years has also stepped aside.
Lord Goldsmith was given his peerage and his position by Tony Blair and is a past donor to the Labour party.
Iraq legal advice
It was the Attorney General's role in outlining the legal basis for the use of force against Iraq that first brought the spotlight on the position.
Lord Goldsmith published his full legal advice on the war in 2005 amid speculation he had been "leaned on" by Tony Blair.
Elizabeth Wilmshurst, a Foreign Office legal adviser, had resigned in 2003 over the legality of the war.
The advice was originally kept secret but published after a series of leaks during the run-up to the 2005 election.
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