Diane Abbott has dropped a complaint against The Mail on Sunday after she falsely claimed our report that she mistakenly used a gents lavatory in the House of Commons was ‘fabricated’.

The Shadow Home Secretary backed down after a witness gave a detailed account of how Ms Abbott had ‘stumbled’ into the men’s lavatory and acknowledged him as he stood at a urinal – before entering one of the cubicles. It happened at about 10pm on June 11 after Ms Abbott dined in a nearby Commons restaurant in Portcullis House, where many MPs have offices.

This newspaper reported the incident in the Black Dog political diary under the headline ‘Diane’s visit to wrong chamber’.

Diane Abbott has dropped a complaint against The Mail on Sunday after she falsely claimed our report that she mistakenly used a gents lavatory in the House of Commons was ‘fabricated’

Our report, which comprised a total of 51 words, said she was seen ‘innocently wandering into the gents in the Commons. After a man standing at the urinals pointed out her mistake, she said “Sorry” – before calmly heading to one of the cubicles and closing the door’.

The item signed off with a wry: ‘These Corbynistas never obey the rules…’

However, Ms Abbott said the article was ‘fabricated and malicious’ and designed to provoke abuse. She made a formal complaint to this newspaper and to the press watchdog, the Independent Press Standards Organisation (IPSO). Her spokeswoman said the item was ‘not supported by any evidence’.

It meant ‘the entire basis of (the) article is fabricated’ and had ‘the sole aim of ridiculing Ms Abbott’.

The Mail on Sunday stood by the accuracy of the story and informed Ms Abbott and IPSO it had received an account by an individual who witnessed the incident and who said he was ‘outraged’ by her denial.

The individual, who is not a politician and had been visiting Parliament, said that at about 10pm on Monday evening (June 11) Ms Abbott ‘stumbled into the gents toilets’.

A witness gave a detailed account of how Ms Abbott had ‘stumbled’ into the men’s lavatory as he stood at a urinal – before entering one of the cubicles in the Commons

He continued: ‘She acknowledged me at the urinals and then went into one of the cubicles. She had been dining in The Adjournment (a restaurant in Portcullis House)… After she finished in the loo she immediately exited via Westminster Tube with her dining companion.’

Ms Abbott said the story breached IPSO’s Editors’ Code of Practice, which states the media must not ‘publish inaccurate misleading or distorted information’.

Her spokeswoman said that by publishing the item ‘without thoroughly investigating its authenticity’ this newspaper had ‘deliberately and with malice attracted harmful and abusive comments towards Ms Abbott’. The MP called for action to remedy the ‘glaring inaccuracies’ of the story.

Ms Abbott has not responded after The Mail on Sunday informed her on June 29 that it stood by the story. IPSO has taken no action.

Absurdly, one of the comments on social media about the article claimed the title of The Mail on Sunday political diary, Black Dog, was intended as racist abuse of Ms Abbott.

In fact, it has been the name of the diary since the paper was launched in 1982 and derives from the term used by Winston Churchill to describe his battle with depression.

Black Dog is known as the best political gossip column in Westminster and regularly pokes fun at MPs from all sides.

A spokeswoman for Ms Abbott declined to comment.