Brown said Sir Keir might have been "too slow to do the right things" but backed him to "clean up the system".

Many Labour insiders say Sir Keir may not be the man to take them to the next election, writes Laura Kuenssberg.

The former ambassador to the US and Labour minister is under investigation for misconduct in a public office.

Cabinet office minister Josh Simons commissioned APCO Worldwide for the investigation in 2023.

The SNP politician was a key figure in the Scottish government's response to the Covid pandemic.