Tulip Siddiq, the Labour MP for Hampstead and Highgate in north London and the Economic Secretary to the Treasury, is under investigation by the Parliamentary Standards Commissioner for not registering rental income from a London property on time.

This makes her the first MP of the new Parliament to face such an investigation.

A Labour Party spokesperson stated that Siddiq will cooperate fully with the inquiry, attributing the omission to an 'administrative oversight.' The watchdog's website confirmed the investigation regarding late registration of interests.

Concurrently, three former MPs remain under investigation for various breaches: ex-Conservative MP Bob Stewart for non-declaration of an interest and lack of cooperation, former Reclaim MP Andrew Bridgen for registration issues, and former Tory Sir Conor Burns for misuse of confidential information.

During the previous Parliament, the Standards Commissioner initiated over 100 investigations, most of which were resolved through 'rectification,' allowing MPs to correct minor breaches.