The Conservative Party has 40% support compared with Labour's 32%, an ICM poll for the Guardian newspaper suggests.
Support has increased during David Cameron's first year
The 3% rise on the previous month means David Cameron ends his first year as leader with the party enjoying its strongest sustained polls in 14 years.
Labour's 32% is unchanged on November. The Lib Dems fell four points to 18%.
More than a third of voters (37%) think the Tories will win the next election, compared with 19% who felt the same in 2002, the poll suggests.
Among Conservative voters the figures suggest that 67% believe the party will be victorious.
About 12% of voters believed the Conservatives would never win again, according to the poll.
The ICM poll questioned 1,006 adults by telephone between 15-17 December.