Keith Vaz, the former Europe minister, has attacked former parliamentary standards commissioner, Elizabeth Filkin, for conducting flawed investigations.

Giving evidence to the Wicks committee on standards in public life, he said that MPs reputations had been harmed by a "flawed and arbitrary process".

"In addition, complaints have been accepted without appropriate screening from bankrupts seeking revenge against former employers who also know the member, and from people who are mentally ill and the subject of secure accommodation orders," he added.

He also called for commissioners to register their interests in the public register "in order to avoid the appearance of bias or assumptions of prejudicial interpretations of evidence".