[2] The Commissioner is the decision-maker in cases from the Independent Complaints and Grievance Scheme where the respondent is a Member of Parliament.

[5] The post was established in 1995 with Sir Gordon Downey as the first commissioner, serving the newly formed Committee for Standards and Privileges.

The second commissioner was Elizabeth Filkin (1999–2002), whose first case involved Peter Mandelson and a large loan which he had failed to declare in the Register of Members' Interests.

Unlike his predecessor he was appointed to a second term, but he did not complete it; he took up a new post at the beginning of 2008 as an independent adviser on ministerial standards to the then prime minister Gordon Brown.

In an article about Lyon's questioning by the parliamentary enquiry into MPs' expenses, Private Eye described him as "feeble" and an "establishment stooge".