Speaking at a constituency event in Kirkcaldy this evening, Mr Brown said that there was "no greater privilege" than representing the people he grew up with, but that the time had come to step away from the forefront of politics.

Thanking friends, family and his constituency for their support, the 63-year-old continued, "I was going to announce my future after the Scottish Independence Referendum but there was still unfinished business.

"I wanted to make certain that changes would happen before I made my decision.

"It's the right thing to do, and we will have a new person, with new ideas, representing the constituency of Kirkcaldy and Cowdenbeath."

However Mr Brown was keen to reassure people that he was not leaving Fife, and would not be heading to the House of Commons or House of Lords.

"Fife is where home is, and it is from Fife where I will do my work as UN special envoy for global education," he added.

Mr Brown also said that he would not be too far away if the country needed him again.

"I've no desire to return to frontline politics," he said. "But if the cause of Scotland in Britain needs friends to speak for it and I feel I can make a difference, I will play my part."

The Kirkcaldy and Cowdenbeath Labour MP was first elected for Dunfermline East in 1983, and became Chancellor of the Exchequer in 1997.

Ten years later he became Prime Minister of the United Kingdom, a position he spent three years in before resigning in 2010.

Since then, Mr Brown took more of a back seat to the political scene, but became involved in the Scottish Independence Referendum debate where he was widely credited with helping to secure the vote to remain part of the UK.

When he retires in May, Mr Brown will have spent 32 years in Parliament, and he thanked his wife Sarah for her support over the years, calling her "incredible."

MSP Alex Rowley said that it was not farewell, and that Mr Brown would continue to influence the politics of Fife and the politics of Scotland.

Fife Provost Jim Leishman added that it was because of Mr Brown that he entered politics and gave an emotional thank you to the former Prime Minister.

Read more reaction in Thursday's Press.