Labour leader Ed Miliband has paid tribute to former energy minister Malcolm Wicks, who has died aged 65.
The Croydon North MP, who had been fighting cancer, was praised as a "thoroughly decent, intelligent and compassionate man" whose death left a "huge hole" in the party.
Mr Miliband said: "He was a brilliant energy minister, he was a deep thinker about welfare and pensions, and Labour to his core.
"Malcolm was also a dedicated constituency MP, always putting the needs of his Croydon constituents first. He was a brilliant campaigner.
"The way he handled his illness tells you everything about the man. He showed huge dignity and also kept on thinking, writing and advising right to the end.
"I have lost a wise confidant and most importantly a dear friend and the Labour Party has lost one of its sharpest thinkers. Our thoughts go to Malcolm's wife, Margaret, and his family."
Mr Wicks represented Croydon in Parliament for two decades and held a variety of ministerial briefs under Tony Blair and Gordon Brown - including pensions, science and energy.
The married father and grandfather stepped down from the government in 2008 and spent two years as the prime minister's special representative on international energy issues. He was also made a member of the Privy Council.
Wicks was re-elected with an increased majority of nearly 16,500 at the 2010 general election.
He is understood to have been unwell for some time.