Labour MP Ashok Kumar has died, his office has said.
He was found on Monday morning at his home in Middlesbrough in what was being treated as a "sudden accidental death."
The spokesman said: "It came as a huge shock to everyone."
Mr Kumar, who was 53, represented Middlesbrough South and East Cleveland.
Fellow Labour MP Sir Stuart Bell, whose Middlesborough constituency neighboured Mr Kumar's, said: "The death of Ashok Kumar at so young an age is tragic.
"He has been for many years a fine parliamentarian and good constituency MP. He built up his parliamentary majority and had every expectation of being returned to the house at the forthcoming election.
"He will be mourned by his many friends and colleagues. He leaves behind an untarnished reputation."
A Cleveland police spokesman said: "At this stage it is too early to say whether the death is being treated as suspicious and inquiries are ongoing."
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