An investigation into the alleged sexual assault of an MP by Boris Johnson’s former Scottish campaign manager has been widened to include a second allegation.

The parliamentary standards watchdog is examining claims that Ross Thomson, 32, fondled Paul Sweeney, the former Labour MP for Glasgow North East, over his trousers at Strangers’ Bar in the House of Commons and then tried to force his hand below Mr Sweeney’s belt.

The alleged incident is said to have taken place in October — eight months after police were called to the same bar to speak to Mr Thomson, amid claims that he was drunkenly groping men.

The Metropolitan Police said then that officers had been called after a “report of sexual touching”, adding that they