The unions urged the nine candidates to commit to fully implementing the recommendations of a hard-hitting report on bullying and harassment by High Court judge Dame Laura Cox last year.

The report found a “disturbing” and “pervasive’ culture in Westminster, and warned that a tradition of deference and silence had prevented victims from speaking out

It said that a small number of MPs were engaged in “predatory” conduct that was too often dismissed as harmless banter. Staff were subjected to “frequent sexual innuendos, lewd comments or sexual gestures”.

After the report was published, Commons bosses agreed to open up historic cases to scrutiny.

But they have so far stopped short of setting up a complaints system “entirely independent” of MPs to assess claims made against them.

The letter from Prospect deputy general secretary Garry Graham and FDA general secretary Dave Penman says: “As trade union leaders representing hundreds of parliamentary staff, we have consistently called for the full implementation of the recommendations made by Dame Laura Cox.

“If you are successful in the contest to become the next Speaker, you will have a central role in restoring this trust, not least by ensuring parliament has working practices and a working culture in keeping with its prominence as the heart of our democracy.”

At the time of going to press, eight of the nine candidates had responded, with all of the frontrunners pledging to implement the reforms and consult unions.

The election for Speaker took place on 4 November after Profile went to press.

Cox report into the bullying and harassment of House of Commons staff – http://bit.ly/cox-report

Download a Zip file with all the responses from candidates for Speaker: https://library.prospect.org.uk/download/2019/01604