UKIP leader Nigel Farage told Daybreak that today's result in South Shields was "remarkable".
He said: "People haven't seen us as being relevant for local elections, or in some ways general elections, so for us to be scoring at least 26% of the vote where we stand is, I think, very significant indeed."
When asked about whether the party had now entered a four-party race, Mr Farage replied: "Numerically we're the third [party] because the Lib Dems are trailing behind."
He added: "This wave of protests certainly isn't short term, it's lasting."
More top news
The Queen and senior members of the monarchy will attend services around the world to commemorate the centenary of the battle of Gallipoli.
The Liberal Democrats have proposed to invest an extra £10 million in mental health care for military personnel
David Cameron hopes to set out a positive vision of Toryism for ethnic minorities predicting the UK's first black PM will be Conservative