Heart patient Anthony Embleton died three weeks after doctors ordered him back to work.
The 38-year-old had been on sickness benefit after undergoing surgery following a heart attack two years ago.
But last month benefits chiefs called him in for an examination and agency doctors declared him fit for work.
They also slashed his £270-a-fortnight sickness benefit to £80 income support.
Mr Embleton, a former groundsman at Brough Park race course in Newcastle, was set to appeal against the decision, but died of a heart attack just over a week ago.
Now his family claims Benefits Agency bosses did not consult his doctor - and say the stress of having his money cut contributed to his death.
His grieving partner of 20 years, Julie Mackintosh, 38, said: "Anthony was worried sick about money and feeling stressed."
Miss Mackintosh has vowed to carry on with the benefits appeal - despite the tragedy.
A spokesman for the Department of Work and Pensions said he could not comment on individual cases.
He said: "Someone receiving benefits because they are incapable of work will eventually be required to attend a medical examination.
"The report of this examination, together with all other available evidence, is used to decide whether that person satisfies the legal conditions for receiving benefit. The customer has the right of appeal."
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