Chancellor George Osborne has warned voters that the 2015 general election will be a two-horse race, between David Cameron and Ed Miliband.
Osborne acknowledged the frustration felt by historically Conservative voters who are considering backing Ukip, but stressed that there are "only two outcomes of the general election".
He said: "A vote for Ukip is a vote for Labour, a vote for Ukip is a vote for Ed Miliband and Ed Balls. They are the people who will run the country if people vote Ukip."
In comments made to Sky News on Monday morning, Osborne stressed that the economy, not immigration, will be the deciding factor in next year's election.
"I completely understand people's frustration on issues like immigration and welfare. But the party that is tackling those problems, able to make a difference, is the Conservative Party."
His words come ahead of his speech at the Conservative Party conference in Birmingham today (Monday), which will begin at 11.30am.
Conservative voters choosing to back Ukip has riled the party in the past week following the defection of Mark Reckless, Conservative MP for Rochester, to Ukip on Saturday.