"Either the party learns that lesson or it dies", Farage tweeted in an apparent reference to Andrea Leadsom, the head of the United Kingdom parliament's lower house, who stepped down on Wednesday saying she no longer believed that the government's approach would deliver Brexit.
The remaining results, in Northern Ireland and Scotland, won't be announced until later on Monday.
The MEPs elected from the South East region are: Nigel Farage, Alexandra Phillips, Robert Rowland and Belinda De Camborne Lucy for the Brexit Party; Catherine Bearder, Anthony Hook and Judith Bunting, Liberal Democrats; Alexandra Phillips, Green; Daniel Hannan, Conservative; John Howarth, Labour.
Both the governing Conservatives and main opposition Labour Party took a drubbing, losing most of the seats held since the last election. Lib Dems second with 11,674, Greens come in third.
The Brexit Party did particularly well in Thanet in Kent, taking nearly half of the vote (49%).
The Lib Dems narrowly triumphed in York with 16,340 votes. May's ruling Conservatives were forecast to get between 10 and 12 per cent of the vote.
Mr Farage has already indicated that he would stand Brexit Party candidates at the next general election. The Conservatives were beaten into fifth place.
A huge majority for the Brexit Party in Medway.
While the Brexit Party has been registered massive numbers in the first results released, Change UK has performed abysmally, despite promises of shaking up the polls.
Ms Widdecombe said: "It's very clear. there was only ever one reason for voting for the Brexit Party - and that is what the nation has done, big time".
"And those same polls show we would have beaten him by a country mile if we had unambiguously backed a public vote on any form of Brexit".