By Andrew Osborn
LONDON (Reuters) - Support for the anti-EU UK Independence Party hit a record high of 25 percent, an opinion poll showed on Sunday, days after it won its first elected seat in Britain's parliament at the expense of Prime Minister David Cameron's party.
The survey suggested that UKIP, which favors a British exit from the European Union and tighter immigration controls, could pick up more seats than previously thought in a national election next year.
"It is not only our right to seek election into the House of Commons (lower parliamentary house) in May, it has also become our duty to succeed," Nigel Farage, UKIP's leader, wrote in the Mail on Sunday newspaper.
"Too many people have been too badly let down by the political establishment for far too long for failure to be an option."
UKIP's rise threatens Cameron's re-election drive by splitting the right-wing vote, increases the likelihood of another coalition government, and poses a challenge to the left-leaning opposition Labour party in northern England too.
UKIP won its first elected seat in parliament by a landslide in a by-election on Thursday, after a parliamentarian from Cameron's center Conservatives defected and took almost 60 percent of the vote.
It won European elections in Britain in May, has poached two of Cameron's lawmakers since late August, and will try to win a second seat in parliament in a by-election expected next month.
Before Sunday, most polling experts had forecast it could win only a handful of the 650 seats in parliament in 2015.
But based on the result of the Survation poll for The Mail on Sunday, the party could win more than 100 seats in 2015, the newspaper quoted a pollster as saying.
The poll put UKIP's support at 25 percent, 2 percent higher than a similar poll in September.
Support for the Conservatives and Labour was tied at 31 percent, according to the poll, which was based on interviews with 1,003 people nationwide.
Given the country's first-past-the-post, winner-takes-all electoral system, a three-figure seat count for UKIP seems unlikely.
The party itself is aiming for between 12 and 25 seats, and two other polls on Sunday put UKIP's support at 16 and 17 percent.
RECORD POLL RATING
But all three polls underline the party's rise.
In 2010, the last time a national election was held, UKIP won just 3.1 percent of the vote and no seats in parliament.
Labour leader Ed Miliband, whose party came within a whisker of losing a seat in northern England to UKIP on Friday, wrote in The Observer newspaper that he recognized that UKIP was "tapping into a seam of discontent and despair that Labour cannot – and will not – ignore."
Miliband signaled his party would not respond with a knee-jerk policy change, but would stick to its re-election plan to promise a higher minimum wage and more money for the country's health service.
(Editing by Aidan Martindale and John Stonestreet)