Ukip has delivered its strongest performance in local elections after making a series of gains across England.

In the biggest surge by a fourth party in England since the second world war, Ukip averaged 26% of the vote in council wards where it stood, according to a BBC estimate.

With only seven of the 35 council election results declared so far, Labour said it was performing reasonably across the country. The Tories have lost control of two of the seven and the Liberal Democrats have also lost seats, including four in their key target area of Somerset.

The Ukip success saw Nigel Farage's party deprive the Conservatives of control of Lincolnshire county council after gaining 16 seats to become the main opposition. The Tories also lost control of Gloucestershire where Ukip gained three seats and Labour four.

The Tories maintained control in Dorset and Somerset but Ukip won its first seats. The party gained 10 new seats in Hampshire and performed strongly in Essex.

The Ukip success in Lincolnshire saw the party's Richard Fairman unseat Eddy Poll, the Tory deputy leader in Spalding. Kelly Smith, the executive member for finance, and Graham Marsh, who ran adult services, also lost, according to BBC Lincolnshire.

A mother and three daughters – Sue Ransome, Felicity and Elizabeth – won three seats in Boston. Her husband, Don Ransome, who came second in Boston South, told the BBC: "Our time has come – I'm used to always being the bridesmaid – but at least I've got a few brides with me now. Everybody has had enough, and hopefully we can deliver something different – and spend Lincolnshire taxes on Lincolnshire people."

Peter Bedford, a Conservative councillor who lost his seat to a Ukip candidate, said: "It was a protest against central government's polices – it's disappointing but we'll bounce back."

Grant Shapps, the Tory chairman, said: "People sent a clear message. We hear you."

Hilary Benn, the shadow communities secretary, played down the Ukip threat. He told the BBC: "It is a protest party and not a party of government. Its economic policy does not add up."

Professor John Curtice of Strathclyde University said Ukip had achieved a "remarkable performance". In a briefing paper for the Political Studies Association on the local elections, he said Ukip presents the most serious threat by a fourth political force in England since the second world war.

All the seats on 27 county councils (1,811) and all the seats (528) on the six unitary councils were being contested. A third of the seats (23) were contested on six unitary councils. In Wales, 30 seats were contested on Anglesey borough council.

The Tories were defending nearly two-thirds (1,477) of the 2,362 seats up for grabs on Thursday. They expected heavy losses as they defended seats captured when they were at a polling high in 2009.

• This article was amended on 7 May 2013 to correct the number of seats contested on Anglesey borough council from 40 to 30.