The Conservatives say they are "very encouraged" by the latest English council by-election results - in which they took a seat from Labour.
By-elections were held for nine seats
They say they achieved swings that would translate to Parliamentary gains in three seats in a general election.
In nine local by-elections, Labour held six and gained one, the Tories retained one and won one on Sunderland Council.
It follows much speculation that Prime Minister Gordon Brown is preparing to call an early general election.
Labour has enjoyed a poll lead - dubbed the "Brown bounce" - since Mr Brown took over as prime minister in June.
In several seats there was an apparent "swing" from Labour to the Tories - notably in Sunderland's Washington East seat - which the Conservatives won from Labour - which saw a 3.7% swing.
But there were also several swings to Labour - the biggest of which was a 11.6% swing from the Conservatives in Dover District Council's Aylsham ward.
Tory Party chairman Caroline Spelman said: "Labour should be very worried that in a week when Gordon Brown has dominated the news, the Conservatives have made a crucial gain from Labour in the north and achieved a swing in three marginal seats which would mean three strong Conservative gains in a general election."
But BBC political correspondent Sean Curran said it was important to remember that people often voted differently at local elections compared with general elections.
And in some wards results are difficult to interpret because the list of parties standing was different to that from the last local elections. In Mansfield and Chester-le-Street, the Lib Dems had a candidate this time, but did not field one last time.
Labour won one seat, Lindhurst ward on Mansfield District Council, from an independent. It also held six seats - on Kent County Council, Dover District Council, Northamptonshire County Council, Portsmouth City Council and Chester-le-Street District Councils.
The Tories, meanwhile, successfully defended control of Cheshire County Council.
Despite widespread speculation during Labour's conference this week, Mr Brown has repeatedly refused to reveal his intentions for the date of the next general election.
It is believed the prime minister will meet advisers this weekend to discuss the possibility of calling a snap vote.