The rising level of political abuse is fuelling an "atmosphere of increasing hatred" which threatens to poison democratic politics in the UK, First Secretary Damian Green has warned.
Mr Green said that in recent years there had been a "ridiculous" rise in routine comparisons to Hitler and the Nazis as people sought to portray their opponents as "not quite human".
Following the murder last year of MP Jo Cox, he said politicians and journalists needed to be mindful of the impact of their words when they went in "studs up" on an opponent.
Speaking at a lunch for political journalists at Westminster, he said: "If mainstream politicians and journalists start to behave like Twitter trolls and conspiracy theorists then democracy is in danger.
"I do think we need to respect each other motives and treat each other's views with courtesy. If we don't we risk feeding an atmosphere of increasing hatred which at the most horrible extremes led to an event like the killing of Jo Cox."
Mr Green, who strongly criticised websites such as the Canary, Skwawkbox and Breitbart, said the level of online abuse aimed at MPs was "appalling".
He said it did not reflect the reality of life in the House of Commons where MPs frequently worked with political opponents on a cross-party basis.
"I think everyone before they go in studs up on a political opponent needs to think long and carefully about whom they are talking to," he said.
"It might play well with your own troops to give an opponent a big kicking on the latest microsite but perhaps it behoves us all to ask 'who's reading it and what are they going to do next?'
"We have in the past few years witnessed a sad and completely ridiculous rise in routine comparisons to Hitler and the Nazis.
"It is symptomatic not just of a decline, but of a rapidly increasing viciousness in our discourse which is totally out of kilter with what I see day after day in the House of Commons.
"Even when we are in the chamber or on the media giving it what-for, we need to remember that we are all democratic politicians.
"What is pernicious is the attempt to portray your political opponents as somehow not quite human.
"It is the trick of extremists on both sides throughout the ages and we shouldn't allow it to take hold in this country."
In his speech, Mr Green took a lighthearted sideswipe at former chancellor George Osborne, now the editor of the London Evening Standard, who was sacked by Theresa May when she became Prime Minister.
He said that from reading the paper he knew Mrs May was personally to blame for Ben Stokes' nightlife, Hurricane Ophelia, and that as October goes into November the "sun shines for a smaller time every day".
"The Evening Standard, Russia Today with less George Galloway," he said in a reference to the Kremlin-backed broadcaster, now called RT.
He also joked that as the Government's "general fixer" his job was "to make sure that my colleagues stay united and show the public a great unity of purpose, spirit and message", adding: "It's all going terribly well."