Nick Griffin said his election was a "massive breakthrough"
MEPs and candidates staged a walkout as British National Party (BNP) leader Nick Griffin began his European election victory speech in Manchester.
The BNP won 8% of North West votes, making it the fifth most supported party and returning Mr Griffin as one of the region's eight MEPs.
Outside Manchester Town Hall, where votes were counted, hundreds of anti-BNP campaigners staged a protest.
Mr Griffin said his party was "the most demonised and lied about" in Britain.
Angry protesters chanted "black and white to unite" and "smash the BNP", while dozens of police officers patrolled the area.
'Racists in suits'
Inside the town hall, the BNP leader said: "It will be a huge change in British politics.
"The most demonised and lied about party in British politics has made a massive breakthrough."
Mr Griffin believed that the BNP's share of the vote was much reduced because of smear campaigns.
MEP says BNP 'harnesses racism'
He said: "A vicious campaign by regional papers and direct lies by The Sun and the Express reduced the number of people that came out to vote for us."
The Conservatives won three seats, and Labour two, while the Liberal Democrats and the UK Independence Party (UKIP) retained a seat each.
New Health Secretary Andy Burnham, the MP for Leigh, said Labour needed to bounce back from the results.
"We need to concentrate on connecting with the people and to show them that we're dealing with the issues that concern them," said Mr Burnham.
Elected parties proportion of the vote (%)
Conservative: 25.6 (+1.5)
"I'm disappointed to see the BNP gain so many votes as the BNP can't help people in Europe. They are nothing but racists in suits."
A total of 94 candidates stood in the North West and more than 1.65m people from the region voted - a turnout of 31.7%.
Conservative MEP Jacqueline Foster said "a very difficult few weeks at Westminster" had affected voting.
She added: "Clearly the Labour votes collapsed very badly.
"If it had been a general election there would have been an awful lot of seats that actually Conservative MPs would have been elected to."
Re-elected Labour MEP Brian Simpson said "I don't think it has collapsed but clearly it has not been a good night for Labour and we would like to have seen a lot more votes.
Mr Simpson added disillusioned votes had gone to other parties, including the BNP, because of the "economic recession and also MP expenses."
Despite retaining all Liberal Democrat seats, MEP Chris Davies said: "I'd like to have swept the board."