Labour MP Jack Dromey died suddenly in his flat in Birmingham on Friday morning, the shadow minister’s family said.
Dromey, 73, married to fellow Labour MP Harriet Harman, was understood to have died from natural causes.
The politician had represented Birmingham Erdington since 2010 and contributed to a parliament debate as recently as Thursday.
Dromey and Harman’s son, Joe, tweeted: “Our dad – Jack – died suddenly today. We loved him so, so much. Rest in peace big man x.”
A statement issued on behalf of the family of the Birmingham Erdington MP said: “Jack Dromey MP died suddenly this morning aged 73 in his flat in Erdington.
“He had been a dedicated Member of Parliament for Birmingham Erdington since 2010.
“He was a much loved husband, father and grandfather, and he will be greatly missed.”
MPs from across the political spectrum paid tribute to the former leading trade unionist.
Labour leader Keir Starmer remembered Mr Dromey, who was the deputy general secretary of the Unite union before becoming an MP, as having “dedicated his life to standing up for working people”.
“From supporting the strike at the Grunwick film processing laboratory, when he met Harriet, through to being elected to represent Birmingham Erdington in 2010, Jack lived his commitment to social justice every day,” the Labour leader said.
“Jack was recognised for his determination to stand up for his constituents and he was highly respected and warmly regarded across Parliament.
Former prime minister Tony Blair said the MP had “dedicated his life to the service of others” as a “complete stalwart of the Labour and trade union movement”.
The former Labour leader said: “He was also hugely likeable, a very popular colleague and well respected by all who worked with him. Cherie joins me in sending profound condolences to Harriet and all the family.”
Prime Minister Boris Johnson tweeted: “Deeply saddened to hear of the death of Jack Dromey MP. My thoughts are with Harriet and the family, and all those who knew him as a friend. May he rest in peace.”
Commons Speaker Lindsay Hoyle said MPs are in “disbelief that the life-force that was Jack Dromey has died”.
On Thursday, Dromey contributed to a Westminster Hall debate on Afghan refugees in his role as a shadow Home Office minister, to which he was appointed last month.
Born in London in 1948, he had three children with Harman, the former deputy Labour leader who announced last month she will stand down as an MP after the next general election.
They married in 1982.
Former prime minister Gordon Brown paid tribute to Dromey as a “great humanitarian who never stopped fighting for social justice” and said he will be “sorely missed”.
Dromey joined the Labour frontbench as shadow housing minister in 2010 under then-leader Ed Miliband.
Miliband described him as a “heroic fighter for working people”, adding: “He was fearless in the face of the most powerful and tireless in the pursuit of the causes that mattered.”
Dromey also served on the frontbench under Jeremy Corbyn despite supporting Owen Smith in his attempt to replace the then-Labour leader.
Corbyn said he was “shocked at the sad loss” of Dromey, remembering his work for the Transport and General Workers’ Union and on the Grunwick dispute for workers’ rights in the 1970s.
Tributes also came from trade unions, with Unite general secretary Sharon Graham saying: “Jack dedicated his life to fighting for workers and against injustice. His dedication to the Labour movement should inspire us in today’s struggles.”
At the 2019 general election, Dromey defended his seat by 3,601 over the Conservatives in second place. His death means there will be a by-election to select the constituency’s next MP.