The acting head of the UK’s court service has apologised after a black barrister was mistaken for a defendant three times in one day.

Alexandra Wilson, a criminal and family barrister and author of In Black And White, a memoir of her career so far, tweeted that she was “absolutely exhausted” after staff at the court repeatedly failed to recognise she worked in the legal profession.

Her tweets quickly went viral, drawing accusations of racism within the UK’s court system.

Kevin Sadler, the acting chief executive of Her Majesty’s Courts and Tribunals Service apologised to Ms Wilson and said it was “totally unacceptable behaviour” and he would be investigating the role of his staff in the incident.

Ms Wilson said when she arrived at court on Wednesday the security officer first asked for her name so he could find it on the list of defendants.

“I explained I was a barrister. He apologised and guided me through security,” she said.

“At this point I tried to shrug it off as an innocent mistake.”

After meeting with her client, she then tried to enter the courtroom to discuss the case with the prosecutor.

She said: “At the door a member of the public told me not to go into the courtroom. I asked why and she said because it’s a court, only lawyers can go in. She said I was a journalist.

“The usher (the one person who recognised I was a barrister today) said to ignore her and to head on in.

“As I opened the door, a solicitor/barrister said I needed to wait outside court and said the usher (who, btw, was next to me) would come outside and sign me in and the court would call me in for my case. I explained I’m a barrister. She looked embarrassed and said “oh. I see.

“She turned back around and I walked towards the prosecutor, ready to have our conversation. Before I got there the clerk, VERY loudly, told me to leave the courtroom and said the usher would be out shortly. Before I could respond she then asked if I was represented.

“I, AGAIN, explained that I am a defence barrister trying to speak to the prosecutor. She looked at me, said “oh right, ok” and continued with what she was doing.”

Following the incidents, Ms Wilson said she has lodged a formal complaint: “This really isn’t ok though. I don’t expect to have to constantly justify my existence at work.”

Mr Sadler responded to Ms Wilson’s twitter thread and said: “I’m investigating the role of my staff and contractors as a matter of urgency. This is not the behaviour anyone should expect and certainly does not reflect our values.”

Amanda Pinto QC, chair of the Bar Council, called the incident “appalling”.

She said: “With regret, I fear Alexandra’s experience is not a one-off. Many barristers have to put up with the prejudiced assumptions of others – Alexandra has done so with exemplary grace and patience. I am speaking directly with HMCTS, the senior judiciary and the CPS immediately, urging more to be done to stamp out this behaviour.

“The barristers’ profession is always striving to be more representative of the society it serves. There is more to do to change the perception of the Bar, but that is no excuse for the kind of attitudes and remarks described. We are not all white, middle class men.

“We come from diverse backgrounds and have made it to the Bar on merit, not who we know. Clearly more needs to be done now by those working alongside barristers to guard against anything like this happening again.”

It comes after official figures revealed people from black, Asian and minority ethnic (BAME) backgrounds are less likely to be successful when applying to become a judge, and only 9% are senior barristers.

Last week a Ministry of Justice report found BAME people “over-represented in applications for judicial appointment” but are “less likely to be successful”.

Industry leaders have called for the legal profession to diversify to better represent the public.

“Racism has no place in any part of our legal system – including law firms, barristers’ chambers and the courts,” said Law Society of England and Wales president Simon Davis.

“This type of prejudice highlights the need for us all to reflect on the actions we can take to tackle discrimination.

“The Law Society is in the process of conducting research into the experiences of our black, Asian and minority ethnic members, including the impact prejudice can have on their confidence, career satisfaction and progression, and how we can drive change.

“We all need to play our part in building a more diverse and inclusive legal profession and combating any instances of racism or prejudice.”