The chair of An Bord Pleanála, Dave Walsh, is to take early retirement, citing "personal and family reasons".
Alluding to recent allegations of conflicts of interest at the organisation, he said in a statement: "I am confident that the actions being taken by the Board, supported by the Department and the Office of the Planning Regulator, will help to quickly restore the Board's reputation."
The allegations were made against the deputy chair, Paul Hyde, who resigned his position in July but strenuously denied any wrongdoing.
Minister for Housing Darragh O'Brien ordered an initial report to be conducted into the allegations by senior counsel, Remy Farrell.
Mr O'Brien later referred Mr Farrell's findings to the Director of Public Prosecutions, An Garda Síochána and the Standard in Public Office Commission.
The allegations also triggered an investigation by the Office of the Planning Regulator (OPR) which, in the first of two reports, concluded that a renewed code of conduct is "urgently required", along with a new governance, ethics and compliance unit as well as an ethics officer.
In what amounted to a call for sweeping changes, the OPR recommended a quorum of five persons should be mandatory for certain categories of planning decisions.
When it came to board meetings, the regulator's report found that the previous practice of relying on individual board members to present planning cases must cease in favour of presentations being made by the inspector that prepared the planning report.
In a reply which drew sharp criticism from Opposition TDs in the Dáil, An Bord Pleanála said in a statement that it welcomed the Regulator's report, in particular "... the general outcome and review finding which contains no specific criticisms of the Board's practices".
Mr O'Brien subsequently announced a reform plan for An Bord Pleanála, adding the Government was "... making fundamental and legislative changes which will impact on the Board appointment process, structure, capacity and operations".
In his resignation statement today, Mr Walsh said he wanted to recognise "the huge commitment, resilience and expertise shown by everyone throughout the organisation to continue to operate with the highest levels of professionalism, integrity and collegiality in very difficult circumstances".
He said it had been "a privilege" to lead An Bord Pleanála over the last four years.
In a statement, Mr O'Brien today thanked Mr Walsh for his service which spanned 27 years between the Board and the Civil Service and wished him well for the future.
"Minister O'Brien will now move swiftly to initiate the process of appointing a new Chairperson and will also appoint a Deputy Chairperson as provided for under the Planning and Development Act, 2000," a statement said.
"Critical reforms are required to strengthen the Board’s systems and processes and restore public confidence in the Board," it added.
"This will continue to be progressed as set out in the Action Plan for An Bord Pleanála which was recently agreed by Government," it concluded.
