Garda Commissioner Noirin O’Sullivan has announced she is retiring from the Garda today.

In a statement, Ms O’Sullivan said she was stepping down because of the “unending cycle” of investigations and inquiries meant she could not devote enough time to bring about the “deep cultural and structural” reforms required to modernise An Garda.

“The support for me to continue in the role is evident,” she said. “However, I devoted much of my summer break to considering if continuing would be the right thing to do. It has become clear, over the last year, that the core of my job is now about responding to an unending cycle of requests, questions, instructions and public hearings involving various agencies including the Public Accounts Committee, the Justice and Equality Committee, the Policing Authority, and various other inquiries, and dealing with inaccurate commentary surrounding all of these matters.

“They are all part of a new - and necessary - system of public accountability. But when a Commissioner is trying - as I’ve been trying - to implement the deep cultural and structural reform that is necessary to modernise and reform an organisation of 16,000 people and rectify the failures and mistakes of the past, the difficulty is that the vast majority of her time goes, not to implementing the necessary reforms and meeting the obvious policing and security challenges, but to dealing with this unending cycle.”

She added that she took pride in her work over 36 years of service “despite the unprecedented challenges, controversies and criticisms of the last few years”.

Ms O’Sullivan added that she was not leaving her role to take up another job but would instead take some time with her family. “I may decide to take on some other interesting and exciting challenge down the line,” she said.

Taoiseach Leo Varadkar said “crucial and essential” Garda reform would be discussed at Cabinet this week. Mr Varadkar praised Ms O’Sullivan’s service and said he wished her every success in the future. “As she said in her statement, her decision to retire is made in the best interests of An Garda Siochana and ensuring that it can focus on the extensive programme of reform that is now under way,” he said.

The Commissioner has recently faced opposition calls to step aside amid queries over how she dealt with officers inflating the number of breathalyser tests carried out. Ms O’Sullivan returned last week after a five-week leave of absence.

Minister for Justice Charlie Flanagan said he was appointing Deputy Commissioner Dónall Ó Cualáin Acting Commissioner with full powers with effect from midnight tonight.

“In the coming weeks I will consult with the chair of the Policing Authority about a process to identify and appoint a permanent Commissioner to An Garda Síochána, ” Mr Flanagan said.

He said he would brief the Government at the next Cabinet meeting.

He expressed his “sincere gratitude” to Commissioner O’Sullivan and acknowledged her public service over the past 36 years “which ranged from under-cover detective work in Dublin’s inner city in the 1980s to being appointed to the most senior position in the service in March 2014”.

Ms O’Sullivan has dealt with a wide range of controversies since her appointment, including the recent controversy over inflated breath test figures, the Disclosures Tribunal chaired by Mr Justice Peter Charleton , a Public Accounts Committee investigation into financial mismanagement at Templemore Garda training college