Senior Labour figures have urged the party’s executive not to block Andy Burnham from returning to Parliament if he asks to contest the Gorton and Denton by-election.The Greater Manchester mayor has until 5pm on Saturday to ask for permission to stand in the by-election, with reports suggesting the Prime Minister’s supporters will seek to block his candidacy.Sir Sadiq Khan, the Mayor of London, told the Fabian Society conference he thought Mr Burnham should be allowed to stand and would campaign for him.