The head of the banking industry's lobby group UK Finance has quit over "unpleasant" comments in 2008 about high profile financier Amanda Staveley.
Stephen Jones was then a senior banker at Barclays, which is being sued by Ms Staveley over a deal struck at the height of the financial crisis.
He is due to give evidence in the court case in London next month.
Mr Jones said in statement he has apologised to Ms Staveley and feels it is the right time to leave UK Finance.
Her civil lawsuit concerns a multi-billion-pound emergency fundraising for Barclays that was backed by Qatar and Abu Dhabi, which helped the bank avoid the need for a government bailout.
Ms Staveley, currently leading a proposed Saudi Arabia-backed takeover of Newcastle United football club, says her firm is owed money by Barclays for helping to arrange the investment.
Mr Jones's derogatory remarks emerged during written testimony submitted by Ms Staveley's legal team last week. The testimony mentioned "thoroughly unpleasant comments" made by Mr Jones about her to a colleague in 2008.
The submissions also referred to other personal comments by senior Barclays staff of the time, criticising her professional skill and competence.
'Difficult personal decision'
Exactly what Mr Jones said is unclear, but full details of the comments are likely to be read out when he appears as a witness next month.
Mr Jones became the first chief executive of UK Finance when it was set up in 2017 to represent more than 250 of the UK's biggest financial firms.
In a statement on Tuesday, he said: "I have apologised to Ms Staveley and to my colleagues for the comments made in 2008 and feel at this time it is right I step down from my role at UK Finance."
The chairman of UK Finance, Bob Wigley, said Mr Jones had "rightly acknowledged" that the comments were inappropriate and "do not meet the standards expected of leaders in our industry".
Mr Wigley added: "He has characteristically taken a difficult personal decision in the interest of UK Finance and the industry and we accept his decision."
Ms Staveley, whose private equity firm PCP Capital helped arrange the investment from Abu Dhabi, is claiming up to £1.5bn in damages. Barclays has dismissed the case as misconceived and without merit.