Former Labour MP Marsha Singh has died four months after quitting the House of Commons due to poor health.
The 57-year-old served as a ministerial aide and worked on the Home Affairs Committee, having first been elected to represent Bradford West in 1997.
His resignation in March saw Respect's George Galloway take the seat, overturning Labour's seemingly comfortable 6,000 majority.
Labour leader Ed Miliband called him a "tireless" campaigner.
Mr Singh, who leaves two children and two stepchildren, grew up in Bradford.
Mr Miliband said: "I was very sad to learn of Marsha's death. He was a tireless representative of the people of Bradford West.
"Politics gave him the opportunity to make a positive difference to the community he grew up in and was so proud of. To him, it was a privilege to represent them. And while I know he was sad to leave Parliament in 2012, he did so for the right reasons.
"I send my deepest condolences on behalf of the Labour Party to his family and friends."
Shadow business secretary Chuka Umunna wrote on Twitter: "So sad to hear of the death of our colleague and friend. All our thoughts go out to his family at this difficult time."
Mr Singh had been a ministerial aide and served on the home affairs and international development committees.
When stepping down, Mr Singh told a newspaper that his proudest achievement had been his Community Care (Residential Accommodation) private member's bill in 1998 - restricting the amount of capital a local authority can take into account when deciding whether someone is entitled to residential accommodation.
His seat had been in Labour's hands for 38 years before Mr Galloway's by-election victory in May.
Mr Galloway said: "I can't tell you how sad I am to hear of Marsha Singh's death and my condolences and best wishes go out to his family.
"I didn't know him well personally but colleagues in the House and the staff regarded him as a real treasure. He was well-liked and well-respected.
"I've inherited his parliamentary seat and I will do all I can to honour and respect his legacy. Once more, my thoughts are with his family."