Labour is looking into allegations that members of the public are unable to contact one of its MPs.
Fresh questions were raised after the Evening Gazette in Middlesbrough said it made 100 phone calls to local MP Sir Stuart Bell without anyone answering.
But Sir Stuart told BBC Radio Tees that every answerphone message left for him was responded to.
The MP has previously admitted to not holding constituency surgeries since receiving violent threats 14 years ago.
The newspaper reported: "He says he meets with members of the public by appointment instead, and says people can reach him at any time by telephone.
"To test the claim, the Gazette has been making daily calls to Sir Stuart's Westminster office and Middlesbrough home over the course of several months.
"Despite making a total of 100 calls, no one ever answered."
Sir Stuart told the BBC that he was he was puzzled by the claims.
"We have absolutely no record of this person calling. It is a total mystery to me," he said.
"We do have answer machines because we get so many calls but every call that is made and every message that is left is responded to.
"We have three staff who work full-time on handling constituency matters - letters, emails, text messages, personal interviews.
"I meet people every Friday in Middlesbrough, I go to their homes, I'm on the council estates."
Sir Stuart is understood to have met Labour chief whip Rosie Winterton on Wednesday afternoon to discuss the claims.
He is expected to write to Labour leader Ed Miliband setting out his position on contact with constituents.
A Labour Party spokeswoman said: "Ed Miliband and the Labour Party expect the highest standards from Labour representatives.
"It is totally unacceptable if the public cannot reach their MP. A number of allegations have been raised and these will be discussed with Sir Stuart."
The 73-year-old MP has represented Middlesbrough since 1983.