The City regulator's retail chief yesterday became the only high-profile head to roll over the Northern Rock debacle, but he departs with a payoff of almost £400,000.

The Financial Services Authority (FSA) said that Clive Briault, the managing director of its retail business unit, would leave the regulator “by mutual consent” at the end of April.

Mr Briault headed the team that monitored Northern Rock, which last year suffered Britain's first bank run in more than a century and was forced to borrow £25 billion from the Bank of England.

Rock's chairman and its chief executive resigned shortly after the bank's near-collapse, but until yesterday no senior regulator or politician had lost office over the affair.

The FSA has admitted that it did not undertake an in-depth assessment of Northern Rock for 18 months before it ran into trouble. The regulator is due to release an internal report on mistakes it made in monitoring the bank by the end of this month.

Mr Briault is expected to receive £380,000 under the terms of his contract, which entitles him to a year's pay if his tenure is terminated by the FSA. He has also accrued a pension pot worth more than £870,000.

Hector Sants, chief executive of the FSA, said: “Clive has been an outstanding colleague who has contributed much to the organisation.”

David Kenmir, formerly the managing director of regulatory services for the FSA, will take over Mr Briault's role until a replacement is found. Kathleen Reeves, the FSA's human resources director, will carry out Mr Kenmir's job in the meantime.

Within Mr Briault's division, David Strachan had been responsible for supervising large retail groups, such as Northern Rock, as well as looking after financial stability. Yesterday he was removed from the role.

Mr Sants said that he would, from April 7, split the jobs so that Mr Strachan concentrates on financial stability and Clive Adamson takes on supervision of big retail groups in an acting capacity. The FSA said that it would advertise immediately for a permanent apppointment.

Mr Briault's departure is one of several senior management changes in the FSA since Rock's problems emerged last September. Sally Dewar, formerly the director of markets for the regulator, moved up to become managing director of wholesale. Alexander Justham, who joined the FSA from JPMorgan Chase last year, took Ms Dewar's previous role.

The regulator also created a new prudential risk division, with Colin Lawrence, formerly a risk manager for IBM, as its director. Paul Sharma, an FSA employee, was promoted to be director of wholesale and prudential policy.

Of the seven FSA supervisors who worked closely on Rock before its implosion, five have since left the regulator, the FSA admitted last month after a Freedom of Information Act request from The Times.

At hearings of the Commons Treasury Select Committee after Rock's near-collapse, Mr Sants admitted that the FSA's regulation of it was unacceptable. The FSA's supervisors had not taken sufficient steps to prevent Rock's unusually high reliance on the wholesale money markets, rather than on depositors, for its funding.

Since its emergency borrowing from the Bank of England, Rock has been nationalised and the Government has underwritten almost £100 billion of liabilities held by the bank. The FSA's report on its role with Rock is being written by Rosemary Hilary, the regulator's internal auditor. Some details will be not be made public to protect employees' rights and to respect the confidentiality of rival banks examined for purposes of comparison.

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