Law Society chief executive Catherine Dixon has resigned after just two years in the role over a lack of progress in attempts to reform its governance.

In a letter to the Law Society's governing council, Dixon said that she "cannot in good faith continue to be CEO of an organisation which is not prepared to change".

Dixon, former chief executive of the NHS Litigation Authority, has been CEO of the Law Society since January 2015. She succeeded Des Hudson, who had held the post for eight years.

The Law Society began a review of its governance in early 2016. An initial report, published in May, proposed trimming its 100-strong council and limiting terms for the elected positions to six years. It also recommended that a smaller main board be established to handle most governance decisions.

However, the Law Society's council recently voted against limiting terms and decided not to begin implementing a new main board until council seats have been reviewed, resulting in further delays.

Dixon, who last month was appointed to a panel of experts to help advise the Mayor of London on Brexit, said in her letter that she wanted the organisation to be "less bureaucratic" and that it "'cannot operate in a responsive and agile way" without reform.

The Law Society is under threat following proposals to radically overhaul the regulation of lawyers in England and Wales. Last September, the Legal Services Board unveiled plans to create a single legal services regulator and cut all links between regulators and representative bodies such as the Law Society. The move is supported by the Solicitors Regulation Authority.

"If the external environment was not so hostile, the Law Society could take its time to review its governance and make any changes at its own pace. However, the organisation does not have this luxury," Dixon added in her letter of resignation. "Others are intent on harming it and the profession it serves. We should not give them any ability to be critical of us – and yet we have, as our failure to change means that we don't have the right governance arrangements to enable us to effectively respond to this hostile environment, leaving us vulnerable at this critical time."

Law Society president Robert Bourns said in a statement that the organisation is "extremely grateful" for Dixon's "tireless and effective work" as CEO, and that he noted her comments on the pace of the governance review. "It is important that we press on with changes in order to take the organisation and the profession forward," he added. "I aim to use the rest of my presidency to help drive the next stage of the review and propose further changes."