George Hamilton, who was appointed chief constable in June 2014, said he informed the Policing Board of his intention to leave the service in June.
A police officer for nearly 34 years, he said the greatest privilege of his career “had been to serve as chief constable”.
He said NI was a “much more peaceful and progressive society” than it was when he began his police career.
The announcement has come as a surprise to the chief constable’s senior colleagues and members of the Northern Ireland Policing Board.
He had been expected to accept a three-year contract extension that was offered when he met the board last week.
His decision to decline the offer followed discussions with his wife and four children over the Christmas period.
Sources say George Hamilton broke the news to his senior command team this morning and then informed the board chairman, Anne Connolly.
He told them he is retiring to spend more time with his family.
No current member of the PSNI command team can apply to succeed Mr Hamilton as chief constable.
The current eligibility criteria states that an applicant must have completed a national senior command course and served at least two years in a police force outside Northern Ireland.
After joining the Royal Ulster Constabulary (RUC) – the predecessor of the Police Service of Northern Ireland (PSNI) – in 1985, he worked in a number of roles including a stint as assistant chief constable of Strathclyde Police.
“I am privileged and humbled to have led the dedicated officers and staff of the PSNI and to have worked in partnership with so many people committed to public service in Northern Ireland and beyond,” said Mr Hamilton.
He said that there were challenges in the months and years ahead “but we have overcome greater challenges in the past and there is nothing that cannot be achieved if the police, our partners and the community continue to work together”.
Anne Connolly says the board needs to put in place a process for the appointment of a new chief constable
Anne Connolly, chairwoman of the Northern Ireland Policing Board, said the board respected Mr Hamilton’s decision not to accept a three-year contract extension last week.
She said recruitment for a new chief constable would be considered at a meeting on 6 February.
The Policing Board was established as part of policing reforms after the 1998 Good Friday Agreement, which helped bring about the end of the Troubles in Northern Ireland.
George Hamilton’s police CV
1985: Joined Royal Ulster Constabulary (RUC)
1994: Promoted to RUC inspector and seconded to England for development programmes
1997: Returned to uniform patrol in NI and subsequently worked on Patten policing reforms
2002: Worked as a senior detective in PSNI’s Criminal Investigation Department (CID)
2007: Appointed district commander for south and east Belfast
2009: Joined Strathclyde Police as assistant chief constable
2011: Returned to NI as PSNI assistant chief constable
2014: Appointed PSNI’s fourth chief constable
With many thanks to: BBCNI for the original story
Four RUC/PSNI officers have been disciplined for their involvement in a fight in a bar in Coleraine in 2015.
An investigating officer has also been disciplined.
The fight started in the toilets of a pub in Coleraine and continued in an alleyway outside after those involved were asked to leave.
Four members of the public were arrested at the scene after off-duty officers made 999 calls. Two others were arrested in the following weeks.
They were charged with public order offences and a file was sent to the Public Prosecution Service (PPS).
The off duty officers, who were initially treated as witnesses, were then interviewed as potential suspects after allegations were made against them.
The Northern Ireland Ombudsman found that the investigating officer failed to properly challenge the off-duty officers about inconsistencies in their accounts.
The PSNI accepted the findings of the Ombudsman.
‘Internal disciplinary process’
It was also found that the investigating officer failed to make full use of CCTV and mobile phone footage and was a month late in submitting the file, which meant the officers could not be considered for prosecution.
The investigating officer denied showing favouritism towards the off-duty officers.
After completing its enquiries, the Ombudsman’s office submitted files to the PPS. It directed that the four off-duty officers should not be prosecuted for attempting to pervert the course of justice and that neither they or the investigating officer should be prosecuted for misconduct in public office.
It also suggested that while the test for prosecution had been met in relation to the officer who improperly accessed police records, a disciplinary sanction would be more appropriate.
PSNI Chief Inspector Mark McClarence said the police and the public expect police officers to behave “professionally, ethically and with the utmost integrity at all times, whether on or off duty”.
“Where it is perceived that conduct falls short of these high standards, it is right that officers should face an impartial, thorough investigation by the Police Ombudsman’s office,” he added.
“We self-referred this incident to the Police Ombudsman’s Office for an independent review of the investigation.
“The PSNI accepted the findings of the Ombudsman in this case and implemented an internal disciplinary process which resulted in the officers receiving a misconduct outcome.”
With many thanks to: BBCNI for the original story