With 13 seats up for grabs in the Norwich byelection today, the Greens have a good chance of becoming the largest party

Norwich byelection could give Greens control of a council for the first time

The Green party is hoping to become the largest party in a town hall for the first time as voters go to the polls today in a council byelection with 13 seats up for grabs.

Today's poll of a third of seats at Norwich city council comes on the eve of the Green party's four-day annual party conference in Birmingham, where delegates are hoping to hail a double first for the party this year following the election of their first Green MP, Caroline Lucas, in May.

The scale of the byelection makes today's poll the biggest test of public opinion since the coalition government was formed after the May general election.

The Greens, who currently have 109 councillors elected across 40 local authorities, are hoping to receive a boost from Lib Dem voters disillusioned with the party's decision to join the Conservatives in government.

Most of the ward seats up for grabs are in south Norwich, where the Lib Dems' Simon Wright won the parliamentary seat at the general election by a narrow majority of 340 votes, ousting former Labour minister Charles Clarke, who came second.

Norwich city council is currently run by minority Labour administration, but Labour and the Greens are neck and neck, with nine councillors each. The Liberal Democrats and Conservatives have four seats each.

The Greens are defending four council seats at today's poll, and have set their sights on gaining up to four more.

In a move that may appeal to traditional Labour voters, the Greens have pledged to return inhouse some council services outsourced by Labour.

Adrian Ramsay, who is a city councillor as well as serving as deputy leader of the Green party, said: "It is an exciting time for the Green party. People are responding positively to the work we have done and we stand a good chance of becoming the largest party."

Ramsay stood as the party's candidate for Norwich South at the general election, where he came fourth.

Darren Johnson, a Green party member of the London assembly, said his experience of canvassing local Norwich voters suggests that the Greens could be the beneficiaries of disgruntlement with the Lib Dems in coalition.

Johnson, who was in Norwich last week, said the race would be close: "It clearly seemed like a two-horse race between the Greens and Labour. Support for the Liberal Democrats seems to have completely evaporated and both they and the Conservatives seemed extremely unpopular with local voters."

The unusual timing for today's elections in Norwich is due to a decision by a high court judge to cancel the previous government's plans for unitary status for Norwich.

The decision to grant unitary status to the city council gave the 13 councillors who should have stood for election this May extended terms of office until May 2011.

At the time, Labour held 15 seats, the Green party 13, the Lib Dems 6 and the Conservatives five.

But the decision was formally quashed by the high court at the beginning of July, and as a result the 13 seats became vacant.