Four Labour candidates were returned shortly after 3am after a marathon wait – thanks to the borough of Tower Hamlets taking so long to count its votes.
The lone London Liberal Democrat MEP lost the seat she has held since 1999, the Conservatives lost one of their three MEPs, while Ukip and Greens retained a single seat each.
The long-serving Liberal Democrat MEP Sarah Ludford said she did not blame Nick Clegg's leadership for the party's catastrophic election result, which has left it with just one MEP.
“I think there is only a minority – a couple of hundred people who have signed this petition [calling for Clegg to stand down]. Of course it wasn't Nick Clegg's fault – the whole party has to take whatever responsibility it has to take."
Labour's London result – in which it won 37% and beat the Tories by a massive 310,000 votes – pushed the Conservatives into third place nationally in the European elections.
The Conservatives won 22% in London against Ukip's 17%, followed by the Greens on 9% and the Lib Dems on 7%.
Re-elected Tory MEP Syed Kamall said: "We are a party of government and it's one year before an election so you actually expect people to give you a bit of a kicking but ... you will see that our vote has actually held up nationally."
Gerard Batten, who was re-elected for Ukip, said: “I will be joined by I believe another 23 colleagues in the European parliament and we are all dedicated to the same thing. The primary duty of a Ukip MP is to campaign for Britain to leave the European Union.
“In London my only regret is that we did not get our second candidate elected, but we did double our share of the vote and in a number of boroughs I believe we came second or third at the very least.
"We are going to get people elected to Westminster next time and we are going to hold the balance of power."
Labour's re-elected lead MEP, Claude Moraes, declared an “extraordinary” result for his party, while Labour MP Sadiq Khan, who has been spearheading Labour's campaign in the London area, said the party's performances in London at the local and European elections were its best since 1971.
“We have had a really positive offering here in London. We have argued positive policies, which have had a real cut through.”
Jean Lambert, the returned Green MEP, said she had not prepared a speech as she was not sure if she was going to be re-elected.
“We tried to run a very positive campaign, a campaign that actually looked at some of the issues in the European election. We only ever got asked one question –what we thought of one other party in the competition.
“We are going back to a parliament which has some very big challenges. You have seen some of the parties being elected there and the increase in the number of [votes for] anti-Semitic, xenophobic, racist [parties], and I think that is a challenge for us in terms of championing the diversity of London."
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