Labour MP Jack Dromey died suddenly in his flat in Erdington, Birmingham, on Friday, a statement from the shadow minister's family said.
Mr Dromey, 73, married to party grandee Harriet Harman, was understood to have died from natural causes.
A statement issued on behalf of Mr Dromey's family by the Labour Party said: "Jack Dromey MP died suddenly this morning aged 73 in his flat in Erdington.
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"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."
His son Joe tweeted: "Our dad - Jack - died suddenly today. We loved him so, so much. Rest in peace big man x"
Other Members of Parliament have also paid their respects.
Taking to Twitter, Labour MP for Leyton and Wanstead John Cryer said: "Deeply shocked to hear that my friend and colleague - both as an MP & trade unionist - Jack Dromey passed away suddenly this morning aged only 73.
"I knew Jack for around 17 years & worked with him for 15 of those. This is very sad news. My thoughts are with Harriet and his family".
Solihull MP Julian Knight said: "Deeply saddened to hear of the death of Jack Dromey. He was an incredibly able, conviction politician, who was always polite and a thoroughly decent man. He will be missed and I send Harriet and family my deepest condolences."
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