The letter, also published on Twitter, says: “You have claimed on the record this week that there is ‘no place’ for sexism in politics, and yet there are now serious and credible allegations in the Sunday Times that sexist behaviour has not only taken place in your own office but has been celebrated and rewarded.

“You are ultimately responsible for the culture and activity that takes place within Downing Street under your administration.

“If true, these allegations are not only at odds with your professed opposition to sexism but set a terrible example and must result in further action”, Rayner wrote.

Just last week, Angela Rayner had to speak out after an article appeared in the Mail on Sunday in which newspaper’s political editor Glen Owen said that several Conservative MPs claimed that Rayner tries to distract the prime minister at PMQs by crossing and uncrossing her legs.

The Mail On Sunday article has been widely condemned as sexist and misogynist.

Angela Rayner wants Boris Johnson to answer questions about alleged ‘Sexist of the Year’ award handed out at a Downing Street party