Reed Smith has apologised for the way it handled sexual harassment allegations made by a former employee 15 years ago against an ex-partner who was jailed in September for sexual assault. 

In a statement released today, the firm’s EME managing partner, Tamara Box, said she was “saddened” by the findings of the investigation into its handling of the misconduct allegations against former Member of Parliament Charlie Elphicke.

“Our standards require us to fully investigate all concerns of this nature and take all appropriate action to deal with any concerns we identify,” she said. “The firm’s response in 2005 fell short of this standard and, rightly, we have apologised for this.”

The internal review was triggered after the former colleague of Elphicke spoke to The Guardian newspaper on condition of anonymity, claiming she left the firm’s London office because of his behaviour.

The lawyer, who was in her 20s at the time of the alleged incident, says she complained to another partner about Elphicke's behaviour and was, on reflection, “very disappointed that a formal investigation wasn’t undertaken given the gravity of my complaint”.

Elphicke was sentenced to two years in prison in September after being found guilty of three counts of sexual assault against two women.

Box said: “We are confident that the firm’s current policies and procedures would not allow this to happen now, and we will continue to take all appropriate steps to ensure that our values and standards are met by all who work at the firm. We are fully committed to providing everyone who works at the firm with a positive and professional workplace.” 

Tax specialist Elphicke was at Reed Smith from 2001 to 2005 before spells at Mayer Brown and then Hunton & Williams, where he was head of European tax. He entered parliament in 2010 and came off the solicitors’ roll in 2012.

A spokesman for Elphicke, who is appealing his conviction, told the Guardian the allegations were “false and entirely untrue”.

The Solicitors Regulation Authority (SRA) said it was still looking into the matter before deciding on next steps.

Elphicke’s alleged misconduct took place before the SRA was established and under a different regulatory regime, when there was no requirement for law firms to report misconduct to their professional body, which was the Law Society at that time.

In June, the Solicitors Disciplinary Tribunal cleared Baker McKenzie of mishandling an investigation in 2012 into the behaviour of its then London managing partner, Gary Senior, although the subsequent judgment said mistakes had been made during the investigation.