In a statement, the outgoing Upper Bann MP referenced recent revelations that he had an extramarital affair with his former constituency office worker, the DUP councillor Louise Templeton.

He said his family had given him a "precious second chance" and he had "learned from his failings" and they were looking forward to their future together.

DUP leader Arlene Foster thanked Mr Simpson for his service to the community and for his worked with the party.

David Simpson (60) has been a member of the House of Commons since 2005.

He said: “It has been the privilege of my life, and deeply humbling to represent the people of Upper Bann in the House of Commons for the last 14 years.  During that time, I have always endeavoured to ensure that the priorities of people within the constituency were well understood at Westminster.

"As a consequence of the strong vote in 2017, we have been able to deliver on broadband, health and education within the area.

"In recent times it has been well publicised that I made a mistake that brought hurt to my wife and family as well as bringing heartache to another family.

"These were my mistakes and for them I am truly sorry.  I have learned from my failings and my wife and children have given me a precious second chance and together we intend to look to the future together."

David Simpson began his political career in 2001 when he was elected to Craigavon Borough Council, where he later served as mayor. He then served as an MLA and, later, as an MP.

Following the news of his affair, as revealed in Sunday Life, Mr Simpson resigned from the Orange Order, of which he had been a member for 30 years.

Mr Simpson said friends and colleagues had encouraged him to stand in the December poll, however he decided "this is the right time to pass the baton on".

"I deeply appreciate the support afforded to me by my family, friends, party colleagues and most importantly from the people of Upper Bann who have trusted me to represent them over the last four General Elections," he said.

"I will be forever in the debt of those who helped me over the last fourteen years as Member of Parliament and prior to that as an MLA and Portadown councillor.

"I look forward to helping and supporting the party in other facets in the future."

DUP leader Arlene Foster thanked Mr Simpson for his years of service to the party.

"His service has been characterised by dedication to the people who elected him and his business skills and experience were used to the benefit of Upper Bann," she said.

"I wish him well as he takes a new direction in life and I know that he will continue to use his many talents to the benefit of the party and the wider Northern Ireland cause.”