Labor MP Paul Flynn has died after serving his Newport West constituency for 32 years, his local association has confirmed.
The 84-year-old briefly served as shadow secretary of state for Wales and shadow leader of the House of Commons during his career.
Labor leader Jeremy Corbyn has paid tribute, calling him a "good friend" with a "dry wit" and an "independent thinker".
Paul Flynn. I'm very sad. He had such love for Newport, a knowledge of radical. He was an independent thinker who was a credit to the Labor Party. He will be greatly missed.
– Jeremy Corbyn (@jeremycorbyn) February 17, 2019
Mr Flynn had announced in October he was standing as an MP at the next election two to illness.
Newport West Labor posted on Twitter on Sunday night: "It's with great sadness that we let you know that MP, Paul Flynn, had died today.
"Paul is a hero to be in the Newport Labor family and we mourn for his family's loss.
"We would ask that the privacy of Paul's family be respected at this difficult time."
Mr Flynn was known for his passionate support of the legalization of medicinal cannabis.
First Minister of Wales and Welsh Labor leader Mark Drakeford said the MP was a "giant of the Welsh Labor movement".
He added: "Today's news will be a source of great sadness to all those who knew him.
"He was one of the most effective communicators of his generation, but he was Paul's willingness to speak up for causes beyond the political mainstream.
In the run-up to the devolution era and beyond "I first met him more than 35 years ago.
Rupa Huq, Labor MP for Ealing Central Acton, said: "Deeply saddened to hear of the passing of Paul Flynn MP.
"We served on @CommonsPACAC together and he was a fearless promoter of the cannabis legalization private members bill."