Bermondsey councillor Denise Capstick - who was convicted of drink-driving earlier this year - is to resign as Southwark's executive member for health and adult social care.
Cllr Capstick, a Liberal Democrat who represents SE1's Grange ward, made a statement announcing her resignation at the start of Wednesday night's council assembly meeting at Southwark Town Hall.
"As members will be aware, in the early hours of May 17 I was caught drink-driving by the police. I have already said how truly sorry I am that I took such a stupid decision to drive my car home that night and for the embarrassment that has been caused to officers and members of this authority. I accept that, even though I was not on council business at the time, my conviction brought attention to the council for all the wrong reasons."
"I have been punished by the courts for my actions. I have been banned from driving for 14 months and been given a fine. As a nurse, this conviction will stay with me for the rest of my working life. It will also have a significant impact on my personal and family commitments."
The incident has since been reported in the national press including the Daily Mirror and Private Eye.
Cllr Capstick told the meeting that she had been "overwhelmed" by the number of her Grange ward constituents and other local residents who had contacted her with messages of support and good wishes.
She also revealed that she has been informed by the Standards Board for England, which oversees the conduct of councillors, that she has "absolutely no case to answer".
"However, I have to acknowledge that, for so long as I remain on the executive, there will be as many comments about me as there will be about our work," said Cllr Capstick, who went on to pay tribute to council officers and primary care trust colleagues.
"I do not want my foolish mistake to detract from their hard work and success so I would like to announce tonight my intention to resign from the executive."
Cllr Capstick will remain in the role – which carries a special responsibility allowance of more than £30,000 a year – until the end of October to allow a successor to be appointed and to handle an ongoing inspection of the council's adult social care provision.
Her statement was met by applause from both sides of the chamber.
Since Cllr Capstick's conviction came to public attention last month, calls for her resignation have been led by Cllr Peter John, leader of the opposition Labour group. He immediately welcomed her statement: "It is the right thing to do," he said.
Capstick's boss, council leader Nick Stanton, paid tribute to her work: "I am very sorry that Denise has felt the need to resign but appreciate the reasons for her decision."
Southwark's Liberal Democrat group will choose its nominee for the health and adult social care portfolio at its meeting in early October.
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