It is believed to be the first instance of a solicitor being struck off for non-criminal sexual misconduct at work, The Law Society Gazette reports.

Oliver Bretherton, who was also ordered to pay £23,500 in costs, was admitted in 2007. He had disputed some of the allegations, telling the tribunal that his relationship with ‘Person A’ was consensual.

The Solicitors Disciplinary Tribunal (SDT) will publish its full decision and reasons in a written ruling later this summer.

Mr Bretherton was found guilty of 70 specific allegations. His conduct was deemed to be sexually motivated in certain instances, constituting an abuse of position and a lack of integrity.

The tribunal heard evidence that Mr Bretherton, who is married, engaged in a “fantasised sexual relationship” with Person A, exchanging WhatsApp messages and sending her a video of himself masturbating. According to the Solicitors Regulation Authority (SRA) during the hearing, he assigned the teenager tasks “relating to his sexual gratification” and said he wanted to have sex with her in the office.

A colleague at the same firm said that Mr Bretherton had referred to Person A as “the fittest” after interviewing her for a role at the firm, and that they were seen flirting during her first week. They later kissed on a night out with other work colleagues.

Mr Bretherton insisted the relationship was consensual, denying any abuse of his seniority. He told the tribunal that he perceived Person A as a mature and confident adult who was “actively encouraging and instigating” their relationship.

Further allegations of misconduct regarding two other women who worked with Mr Bretherton were also proven.

Following the allegations, Mr Bretherton left Gowling to join virtual firm Gunnercooke as a banking and finance partner.

In response to the tribunal’s misconduct findings, David Fennell, Gowling’s chief executive, said: “We are appalled that some of our people had to endure such unacceptable attention from a colleague. Mr Bretherton’s behaviour was abhorrent and bears no relation to the values which Gowling WLG believes in and stands for.”

A Gunnercooke spokesperson confirmed Bretherton’s departure. They commented: “We want to make it clear that there has been no evidence of inappropriate behaviour at our firm, and we have, and always will, take action to protect and safeguard our people, policies and our values.”