DAWN BUTLER has called for the Liberal Democrats to launch an investigation after one of its staffers said her claim about being mistaken for a cleaner was false.

Butler has said that she was once confused for a member of the cleaning staff by a fellow MP because she was black and told that a lift she was using was “not for cleaners”. She most recently wrote about the experience for Metro.

Responding to Butler’s claim, Steve Wilson, who is married to MP Angela Smith, tweeted: “Sorry but this [is] just not true. I’ve worked in parliament for 15 years and the lifts have always been for use of everyone. Only time MPs have priority is during a division.

“Stories like [this] don’t do anyone any justice and anyone propagating [them] should stop it.”

In a letter to Jo Swinson, the leader of the Liberal Democrats, Butler wrote: “I find this trolling deeply disturbing, to be accused of lying about a racist incident I experienced was particularly distressing. This type of “gaslighting” is totally unacceptable and having had a chance to ruminate on the matter, I feel compelled to implore you to investigate this incident.”

Butler added: “This isn’t a ‘story’ or a lie. This is race discrimination in the workplace, it is experienced by black, Asian and ethnic minority people in workplaces across our country on a daily basis and we need to stamp it out.”

The MP for Brent Central urged Swinson to investigate the matter immediately and “take firm disciplinary action”.

Wilson has since apologised.

Earlier this year, during an appearance on BBC Two’s Politics Live, Smith referred to people who are not white as having a “funny tinge”.

The MP for Penistone and Stocksbridge was heavily criticised after making the remark and later apologised for the language she used.

Butler, the shadow secretary of state for women and equalities, has also called on Swinson to look into Smith’s office to assess whether it has a “particular problem” that needs to be addressed through diversity training.