Repeated death threats have forced shadow chancellor John McDonnell to seek police advice about boosting security for his family.
Mr McDonnell said the level of online abuse directed at politicians is "appalling", and they now "get used to" receiving such menaces.
In a wide-ranging interview, he also insisted there is "no way" the Labour leadership would support deselections of moderate MPs and that instead he hopes to persuade prominent centrists back into the front line.
"You get used to death threats after a while," he told BBC Radio 4's PM.
"I had a meeting with the police on Monday morning because I had a couple of emails from someone.
"Once you get one you think 'oh never mind' but once they've followed it up, that triggered the meeting with the cops.
"They came in just to give some advice and they have done this thing about more security at the office and they met my wife just to sort out the security at home.
"It's appalling and it shouldn't be in politics."
A number of Labour MPs have complained of serious online abuse - some from left-wing activists angry over their support for military action in Syria.
Mr McDonnell said "appropriate disciplinary action" would be taken against any party member found to be guilty of such abuse.
And he dismissed the prospect of MPs being forced out by grassroots activists, despite such moves being backed by Ken Livingstone - a close ally of leader Jeremy Corbyn.
"There is no way there are going to be deselections. We would not support them. Quite the reverse: we want people back involved," Mr McDonnell said - including a possible role for former shadow business secretary Chuka Umunna.
"What we are trying to do now is make sure that everyone holds together and confidence in the way forward (by) talking to people all the time.
"When Jeremy put together the shadow cabinet there were some people who refused to serve in positions they had never been offered and on the basis of policies they had never read.
"Chuka and others said they were not going to serve.
"Yvette (Cooper) now is helping us. She has done excellent work on refugees. We are now doing a piece of work on women in the economy.
"I am hoping Chuka will come back and help us on the schools agenda.
"I am hoping that all of them will play a role because a lot of lessons have got to be learned by all of us really."
He said his "door is always open" for advice from former shadow chancellor Ed Balls.
And he said of Tony Blair's New Labour government: "He excluded anyone who disagreed with him. Anyone. The left were removed but even some of the centre-left were removed as well, It was quite an authoritarian regime in many ways and I think that's how you get bad policy decisions."
Mr McDonnell also said he had promised Mr Corbyn not to make any jokes, despite claiming some members of the public enjoyed his decision to throw a copy of Mao's Little Red Book to George Osborne in the Commons.
"I'm reckless with my jokes and I've promised Jeremy no more jokes."
He said of his inability to avoid making a joke: "I think it's because I'm a Scouser."