Democrats have called for emergency hearings in Congress after Donald Trump appointed a vocal critic of the Russia investigation as acting attorney general to replace Jeff Sessions.

Matt Whitaker, Mr Sessions’s former chief of staff, will now oversee Robert Mueller’s probe into 2016 Russian election meddling despite repeatedly criticising the scope of the investigation.

Mr Whitaker was a legal commentator before joining the Justice Department last year, and he echoed the president by warning the probe could become a “witch hunt” and that Mr Trump’s finances should not be investigated, calling that a “red line”.

His new role as acting attorney general gives him the power to reject requests by Mr Mueller, the special counsel, as well as end parts of his investigation, fire him and even keep secret his final report.

The personnel changes, which saw Mr Trump ask Mr Sessions to resign as attorney general just hours after the midterm elections, have triggered fears that the president is moving to restrict the Russia probe.