Furious Lib Dem leaders have called for councillors Terry and Craig Sutton to resign and fight a by-election after they defected to the Tories.

Group leader Martin Hunt said the Suttons had "changed the political map of Colchester overnight" after joining the Conservatives and handing them overall control of the Colchester Council.

"It's been more than 20 years since the people of Colchester have wanted the Conservatives to rule them and as recently as May they rejected the Conservatives once again," he said.

"The decision by the Suttons to join the Conservatives is not just a slap in the face to the residents of Berechurch, who elected them as Liberal Democrats, but to every resident of Colchester, telling them that their votes don't count."

He continued: "If Terry and Craig really think that Colchester needs a Conservative administration, they should have the courage to resign and fight a by-election."

Terry Sutton is not due to stand for re-election until 2010. Son Craig has less than a year left in office.

They quit the Lib Dems last month to become independents after Terry had a fall-out with MP Bob Russell over the new Community Stadium.

Mr Hunt last night said: "Councillor Sutton must accept there are people within the Liberal Democrat group who have concerns about the new community stadium and who respect the MP's right to say what he likes even if we disagree.

"That is not a reason to suddenly take on a new political philosophy."