A last-minute plea has been made to city planners to consider their "awesome responsibility" before deciding the fate of the Oxford prison and castle site tonight.

Edwin Townsend-Coles, a former chairman of the Oxford Civic Society has sent a personal letter to each member of the Oxford City Council's planning committee urging them to think long and hard before backing proposals to convert the historic site into a luxury hotel and leisure complex.

The plan is favoured by the site owner, Oxfordshire County Council, which currently rents it out for use as a film set.

Mr Townsend-Coles, a determined opponent of the £18m scheme, has accused the county of reneging on the opportunity of opening up the site to the public for the first time in decades.

In the letter he said: "Whether the site is retained as one for the people as a whole at which a variety of activities could take place, or is to be leased away for generations to come as a ghetto for the wealthy, now rests on a decision by the city planning committee.

"My appeal to you is to give yourselves time to reconsider the whole enterprise. There is no necessity to make the final decision now."

Mr Townsend-Coles argues that luxury hotel owners would not welcome wandering tourists, parties of schoolchildren, or city workers enjoying their lunch hours in a traffic-free space close to the centre.

"You have an awesome responsibility - to protect our rights, or sell them away, not for a period, but for eternity," he said.