Poole’s hung council has been left even more finely balanced after a Conservative councillor’s defection to Poole People.

Parkstone ward member Sally Carpenter’s shock rebellion leaves the Conservatives, who form the administration at Borough of Poole, still the largest group with 20 councillors, Liberal Democrats with 18 and Poole People with four members.

However should the Liberal Democrats and Poole Party create an alliance, they could out vote the ruling group, which no longer fields half of the 42 councillors.

Liberal Democrat leader, Cllr Mike Brooke said: “I will not deny that I’m in talks with the Poole People party, because what the Liberal Democrats are interested in is doing the best for the residents of Poole.”

Cllr Carpenter, who was elected in May last year, says she has been frustrated by the strict Tory whip which she feels prevented her from representing the interests of constituents.

“People have a right to expect the councillors they elect to act in their collective best interests. Since my election in 2011, I have been obliged to vote according to the Conservative leadership’s instructions.

“I do not feel this is healthy. The consensus approach of Poole People will better serve the residents and businesses of our borough,” she said.

Welcoming her, Poole People leader, Cllr Mark Howell said his group did not force councillors to vote in any particular way.

He said: “Our position is that we will not enter a coalition with one party against the other. We are, however, prepared to work with any party which does not enforce a whip, or councillor who rejects the party whip.”

Council and Conservative group leader, Cllr Elaine Atkinson said she had accepted Cllr Carpenter’s resignation and: “I will be working with the other party leaders to work out the best composition for the council to move forward.”

She said she would be continuing with the work of leader, explaining the budget at area committees this week, and denied Cllr Carpenter had ever been instructed how to vote.

“I don’t believe we have a whip in the way it’s being suggested. All decisions are made democratically within the group,” she said.