AM Rhodri Glyn Thomas, who has held the Carmarthenshire East&Dinefwr Assembly seat for Plaid Cymru since 1999, will not be seeking re-election in 2016.

Speaking exclusively to the Guardian, Mr Thomas said: “I’ll be 63 by then and it’ll be time to pass on the baton.”

His impending departure could pave the way for ex-Plaid Cymru MP Adam Price to make a dramatic return to Welsh politics.

Mr Price, 44, a miner’s son from Tycroes, stood down as Carmarthenshire East&Dinefwr MP in 2010 to spend a year studying in the United States.

Nowunderstood to be acting as an adviser for Plaid leader Leanne Wood, Mr Price – who in 2004 famously tried to impeach the then Prime Minister Tony Blair over his involvement in the Iraq War – could put his name forward for a candidates’ shortlist as early as next month.

Speaking to the Guardian on Monday, Mr Price declined to be drawn on his plans, preferring instead to pay a warm tribute to Mr Thomas.

“Rhodri has been an incredibly effective constituency representative who has provided sterling service,” he said.

Mr Thomas’s proudest achievements were winning the seat for Plaid after the Welsh Assembly’s inception and establishing a Plaid office in Ammanford. More recently he campaigned successfully for the Welsh Government to make up a 10 per cent funding cut in council tax benefit.

Mr Thomas’s low point came when he resigned as Heritage Minister in 2008 after being seen with a lit cigar in a Cardiff pub. A few weeks earlier he had been criticised for reading out the wrong name of the winner of a literary award.

“I misread the card and the incident was captured by a TV camera and replayed endlessly,”

he said. “If it hadn’t been, it probably would only have merited a single paragraph in the next day’s paper.”