Wayne Seaborn, of the St John's Ward, informed South Holland District Council leader Gary Porter of his decision last Thursday after his letter was published in the Spalding Guardian.

In that letter Coun Seaborn, who won his seat in last May's elections, criticised the cabinet for pushing through the decision to sell the field "without real public consultation" and accused cabinet members of having "elevated egos".

He will also resign from committees – including the development control committee – because committee numbers are allocated based on the proportion of each party in the council.

Coun Seaborn, of Saxon Close, Spalding, said: "I have found in the last year that my conscience and ability to represent electors has been stifled by the obligations of the leading group.

"Ultimately it was the Castle Fields that made me stand up and be counted, and I knew if I did that I couldn't remain a member.

"I was voted in on the Conservative group and intend to still stand up for the people who voted for me with a Conservative bias."

A consultation on the Castle Field has been carried out by Leisure-Net Solutions for the council in which 728 people were interviewed across the district.

But Coun Seaborn believes this number represents a very small minority of the taxpayers of South Holland and added that his views have been backed up by many acknowledgements of support from businesses.

Sports clubs and organisations were also contacted and the council's leisure options working party is planning a series of events to involve residents throughout July and August.

Following Coun Seaborn's resignation the Conservative group has 25 members compared to 11 Independents.

Coun Porter said: "It's a shame to lose a member of the group, especially one who could have worked so positively.

"There was no pressure on him to resign over the letter.

"We have only gone through the first stage of the consultation so for anybody to decide that the outcome is wrong is premature."