Angela Rayner has moved to block Sadiq Khan's chances of return to Parliament by 'blocking him from running as MP while mayor'.
The Deputy Prime Minister has put forward a Bill that would prevent anyone from serving simultaneously as London mayor and a Member of Parliament.
The legislation effectively closes off Sir Sadiq Khan's most direct path back to Westminster, limiting his chances of returning to the Commons before the next general election.
A spokesperson for Ms Rayner's department said the measure, which would also apply to mayors in other cities, is designed to ensure officeholders can 'focus on' their local responsibilities.
Boris Johnson famously held both roles, using the mayoralty as a springboard to the Tory leadership, and Sir Sadiq's career had followed a comparable trajectory, fuelling speculation he might attempt the same.
