Protesters are planning a prolonged campaign of direct action against Oxford's yet-to-be-built Westgate Shopping Centre.

With construction of the £330m mall expected to take three years, protesters tonight threatened to hound the developers "right to the end".

Protests to stop the removal of trees near the Westgate car park last month resulted in several arrests - including Oxfordshire county councillor Deborah Glass Woodin.

But with vast amounts of materials and equipment moving to and from the site, a serious risk disruption has emerged.

Protesters said they had agreed to embrace direct action as a weapon "to force the company behind the scheme to realise there was serious and substantial opposition to it."

Julia Gasper, of Oxford Against Westgate Group, said: "We want to see peaceful but assertive demonstrations to gain public attention.

"I have heard people talking about going further, if peaceful or legal protests do not work.

"I certainly do not want to see any violence or anyone getting hurt.

"But people are angry and there is a degree of frustration with the democratic process.

"The city council has abused our trust and it is time for us to reassert our ownership of the site in question."

Construction work is due to get under way this summer and will continue until the autumn of 2011.

One campaigner, involved in the recent occupation of trees close to the site, said the Westgate construction could become "messy" if developers did not pull back from "an environmental disaster".

Sushila Dhall, the city councillor for Carfax, said: "As a councillor I cannot condone illegal action.

"But I do have sympathy with those talking about direct action.

"People do not want all the extra traffic that would be generated going past their front doors."

Graham Jones, of the city pressure group Rescue Oxford, said: "It would be cause for great regret if this happened.

"The work which is going to last three-and-a-half years is going to be disruptive enough in any case. If protests extended it for six months or even longer it would inflict terrible damage not just on Westgate, but the whole city."

Campaigners fighting the shopping centre also agreed to launch a postal campaign targeting John Lewis - one of the stores in the proposed development.

And they called for shoppers to boycott the new centre when it opened in 2011.

Westgate Partnership spokesman Simon Ward said: "'The new Westgate will not create 10,000 more car journeys per day.

"The new multi-storey car park will not increase the number of parking spaces. We are working with both councils to encourage shoppers to use the enhanced public transport provision, taking advantage of improved park and ride facilities.

A Thames Valley Police spokesman added: "We will facilitate lawful protest should it take place."