The arrest of shadow immigration minister Damian Green and the search of his House of Commons office last week has provoked severe criticism from politicians of all parties, with comparisons being made to Joseph Stalin’s Russia, Robert Mugabe’s Zimbabwe and Richard Nixon’s US.

Mr Green is suspected of the offence of conspiracy to commit misconduct in a public office. The probe is focused on his relationship with Christopher Galley, a junior civil servant who leaked him information that embarrassed the government. Mr Green denies wrongdoing, while Mr Galley has said he acted in the public interest.