Park-and-ride charges in Oxford look set to increase, despite the opposition of police, traders, bus companies and the county council.

The Liberal Democrat and Green alliance, which runs the city council, agreed yesterday to increase parking charges at Seacourt, Redbridge, and Peartree from 50p to 70p. This is in addition to a £1.50 return bus fare.

Parking will remain free at Thornhill in Headington.

The increase, agreed by the highways and traffic committee, is designed to cut the £800,000 a year park-and-ride costs the council.

A proposal earlier this year to double the parking charge from 50p to £1 was scrapped after county council officers opposed the move.

That increase would have reduced the annual costs by £200,000. The 20p increase will reduce costs for the cash-strapped council by less than £100,000.

Cllr Stephen Struthers, the committee chairman, said the increase was a necessary measure to reduce the annual cost of running the park-and-ride car parks.

"I don't think this will lead to much more traffic in the city centre," he said. "The county council could challenge this but I doubt whether it will bother."

Labour member Alan Pope, who proposed an increase of 10p to 60p to cover increasing security costs, said councillors were "selling their souls to the devil", because they had originally pledged not to use park-and-ride charges as a way of tackling budget deficits.

Fellow Labour councillor Gill Sanders said the measure was clearly a revenue-raising ploy and added: "If we go back on our original promise, we can go back on anything. We will lose our credibility with the public."

The vote on the controversial issue was split 6-6 but the increase was forced through by Cllr Struthers, who used his casting vote.

Former Labour Lord Mayor Maureen Christian immediately referred the decision to full council in the hope that it would be overturned.

Bill McCardle, acting chairman of the Thames Valley Chamber of Commerce, wrote to the committee on behalf of the Oxford Central Retail Association to warn that the increase would put the city at a disadvantage compared to rival regional shopping centres.

He added that the move was particularly inappropriate now with roadworks disrupting Cornmarket and Botley Road.