Poll: Britain's Ukip on Course to Win Second Parliamentary Seat

United Kingdom Independence Party leader Nigel Farage reacts with former Conservative MP and UKIP candidate Mark Reckless and newly elected UKIP MP Douglas Carswell in Rochester, October 11, 2014. Luke MacGregor/Reuters

The UK Independence Party (Ukip), which wants Britain to pull out of the European Union, is on course to win its second parliamentary seat as voters desert Prime Minister David Cameron's Conservatives, according to the latest opinion poll.

The ComRes survey found Ukip well ahead of the Conservatives among voters in Rochester to the southeast of London before a by-election next month, with four in 10 of those who voted for Cameron's party in 2010 now planning to switch.

Ukip was on 43 percent, the Conservatives 30 percent and the opposition Labour Party had 21 percent, the poll found. The election was triggered by the decision of sitting lawmaker Mark Reckless to defect to Ukip from the Conservative Party.

Two weeks ago Ukip won its first elected seat in parliament when another Conservative defector Douglas Carswell won a landslide victory in the seaside town of Clacton.

Nationwide polls have shown support for Ukip, which backs tighter immigration controls along with an EU exit, reaching a record high of 25 percent.

Its rise increases the likelihood of another coalition government, threatening Cameron's re-election drive by splitting the right-wing vote, but also posing a challenge to the left-leaning opposition Labour party in its traditional northern England heartlands too.