Selby's first Labour MP has announced he will not contest the seat for the party at the next general election.
Mr Grogan became Selby's first Labour MP in 1997
In a letter to local party members, John Grogan said his decision had been prompted by his constituency being split in two by boundary changes.
Elected in 1997, Mr Grogan says one of his key achievements was helping miners find work after the Selby pits closed.
He has gained a reputation for being outspoken, opposing the government on several occasions.
Mr Grogan voted against military action in Iraq and university tuition fees as well as opposing the government on nuclear power and religious hatred laws.
However, in his letter, he stressed that he remained "as committed to the ideals and values of the Labour Party as on the day I started campaigning".
At the 2005 general election, he retained the marginal Selby seat by just 467 votes, a result only confirmed after a recount.
At the next election, part of the existing Selby constituency will be in the new Selby and Ainsty constituency, and part will become York Outer.
In his letter, Mr Grogan said: "If the boundaries of the Selby constituency had remained the same I would certainly have sought re-selection.
Coal production at Selby's Riccall colliery ended in October 2004
"However, to do justice to a campaign in either of the successor constituencies... would require spending a lot of time in the coming years campaigning in areas I do not currently represent.
"I would prefer to spend my remaining time as Selby's MP trying to finish the job in a constituency whose electorate, somewhat against the odds, have three times given me the honour of being their MP."
John Tiplady, Labour party agent in Selby, said: "When John was selected in 1985 Labour was a distant third in the area.
"Through his persistence and determination he became the first ever non-Tory to speak for Selby, Tadcaster, Sherburn and the surrounding villages in the House of Commons.
"He has established himself as a strong, independent-minded, common sense and progressive voice."