At least 24 MPs have received identical death threats recently, former Labour frontbencher Chris Bryant has said.
Mr Bryant said the MPs - from various political parties - had been sent the same email threat with a photo of a beheaded person and a message saying they and their families would be killed.
Mr Bryant told the Press Assocation: "In the last year, there has been a slew of these, I've received five or six so far this year.
"It is difficult to know how seriously to take them, but when they mention your family, you have to take them seriously."
The Welsh MP said that he was increasingly concerned about threats to MPs after the death of Labour MP Jo Cox in June.
"It seems that women MPs, ethnic minority MPs and gay MPs get targeted the most," he said.
Mr Bryant, a vocal critic of Jeremy Corbyn, said there was no suggestion the threats are anything to do with the Labour leadership race, but he believed Mr Corbyn had not done enough to stop bullying in the party.
"I think Jeremy has been very slow to take a clear line on this," he said.
He also added that the Labour leader's "digital democracy" strategy, which launched on Tuesday, was out of date as it did not address anti-bullying measures on social media.
When asked why there was no reference to online trolling in the digital agenda paper, Mr Corbyn insisted that Labour had strict anti-bullying rules.