Emily Thornberry is at risk of losing her seat to the Liberal Democrats due to Labour’s ambiguity over Brexit, it was claimed on Tuesday, as Jeremy Corbyn faces his own “Ed Balls” moment.

The shadow foreign secretary, who is seen as a potential successor to Mr Corbyn by party moderates, is said to be one of several candidates deemed “at risk” in London.

Ms Thornberry’s Islington South and Finsbury constituency, which neighbours Mr Corbyn’s seat, is one of the most pro-Remain constituencies in the country and would be considered a major scalp for the Lib Dems.

A senior Lib Dem source told The Telegraph they had seen a significant swing away from Labour in recent months due to concerns among Remain voters over Mr Corbyn’s approach to Brexit.

They added that the Lib Dems were heavily targeting her seat, having repeatedly deployed poster vans in the area, as well as launching the official party slogan there last week.