Chuka Umunna has attacked Jeremy Corbyn supporting "trolls" who criticise Labour MPs who do not offer unqualified support to the Labour leader.
The former shadow cabinet minister also said on Friday that Labour MPs should be given a free vote on whether to take military action against Isis in Syria if David Cameron asks for parliamentary approval.
He also took a swipe at Corbyn's suitability for office given his views on national security. "If you cannot keep the people safe, in their eyes that is a disqualification from office," Umunna told BBC Radio 4's Today programme.
Umunna said: “I have a point of view which I have by reference to my principles and my values and my desire to keep the people that I represent safe.
"And I’m sorry, that will come before any internal party-political issue and I think I should be able to adopt that position without being attacked, without being subject to a nasty troll-form of politics.
"If the new politics is to mean anything, people should be allowed to air their different views on different policies without being insulted, without being trolled, without being threatened with deselection by others in the party and that is unfortunately happening and we need to end that."
Corbyn has long opposed expanding British military strikes against Isis from Iraq into Syria - something Cameron is pushing for.
Several Labour MPs are likely to back the prime minister but to do so without formally rebelling, Corbyn would need to grant them a free vote, something he appears reluctant to do.
Umunna said: "The reality is, on some issues you agree that you cannot always agree. That is why I think it is absolutely fundamental that we have a free vote when that comes."
Also today, former Labour home secretary John Reid told the BBC that Corbyn was not "competent" on security issues.