Who is the current parliamentary standards watchdog?

Sir Philip Mawer. He was appointed from 1 March, 2002, for a three year period.

What is his main role?

His role is basically as a House of Commons "sleazebuster". He receives and - if appropriate - investigates complaints about MPs who are said to have broken Commons rules.

The most high profile complaints tend to be about MPs' financial arrangements - he keeps and monitors the operation of the register of members' interests, which is where MPs declare other employment, property and gifts.

How long does an inquiry last?

How long is a piece of string? Where he decides there is a case to be investigated the process could take a year or more.

Sir Philip said he does not regard the allegations against Iain Duncan Smith as substantiated but argued he needed additional information to evaluate them.

What other responsibilities does the commissioner have?

Amongst other things he is also responsible for keeping and monitoring the register of interests of MPs' secretaries and research assistants - and register of journalists' interests.

Who has Sir Philip investigated?

Michael Trend, MP for Windsor, was recently suspended from the House of Commons for two weeks after he wrongly claimed more than �90,000 worth of expenses.

Do complaints have to come from a fellow MP?

No. A complaint can be made by anyone. For instance, the inquiry into Mr Trend came after he received a letter from piano teacher Roy Birmingham, a Windsor constituent, complaining about the expenses claim.

That followed a newspaper article alleging Mr Trend had wrongly claimed the expenses.

What could happen if a complaint is upheld?

The committee could call on the MP to make a public apology to the Commons. In a more serious case, it might recommend the MP be suspended for a specific period.

In exceptional circumstances, it could press for the MP to be expelled. Suspension or expulsion must be debated and approved by the Commons.

Who was Sir Philip's predecessor?

Elizabeth Filkin left her job as Parliamentary Standards Commissioner in February 2002, complaining that she was the victim of a whispering campaign.

She claimed MPs had tried to intimidate her and witnesses in her investigations.

She also reported that her findings against five government ministers were watered down by MPs on the select committee on standards and privileges.

Her resignation in part prompted the Committee on Standards in Public Life's inquiry into whether regulations governing MPs are adequate to ensure the highest standards of propriety.