Rishi Sunak is facing demands to sack his deputy prime minister Dominic Raab if an inquiry finds him guilty of bullying.
The probe into two formal complaints against the justice secretary is finally under way after Mr Sunak appointed prominent employment lawyer Adam Tolley KC as lead investigator.
Downing Street said Mr Tolley would be given access to witnesses and documents such as emails and WhatsApp messages, and his report would be published in full after its completion.