Developers have halted work towards the new Westgate Shopping Centre - meaning the £330m project will not open in 2011.

Because of a prolonged legal challenge over buying up neighbouring land, the Westgate Partnership has called a stop on preliminary work which started in the multi-storey car park in the autumn.

Westgate Partnerships said it had decided to discontinue until the outcome of December's planning inquiry into the compulsory purchase of surrounding land is known.

The decision had been expected at the end of last month, but the developers now believe they will have to wait until the end of May.

The whole construction timetable has been completely redrawn. The main contract work, planned to begin this summer, will not now be undertaken until early next year.

The centre's opening has been put back to the spring of 2012, nearly two years after the original opening target date.

Opponents of the scheme accused the developers of seriously underestimating the planning complexities of the scheme.

Oxford city councillor for Carfax, Sushila Dhall, said: "They have been doing preliminary work prior to the outcome of the inquiry.

"Until now the developers had just assumed that they would get the go-ahead to demolish the housing in Abbey Place.

"It is proving a more complex issue than they had hoped."

She warned that disabled residents in Abbey Place, who face losing their homes, would take their fight to the European Court of Human Rights if the Government planning inspector did not find in their favour.

But Simon Ward, spokesman for the Westgate Partnership, played down the significance of the rescheduling. He said: "By choosing to defer these works until summer 2008, we are providing further time to progress the detailed design and procurement with our preferred contractor Sir Robert McAlpine.

"The partnership has always anticipated the need for flexibility due to the complexities of a construction project in a historic city centre."

Archaeological work in the multi-storey car park has now stopped, along with the long awaited removal of the derelict Westgate escalators, which have been an eyesore for years. But 100 car parking spaces lost during the archaeological investigations will be reopened to motorists.

Members of the Oxford Against Westgate Expansion campaign are holding a protest "party" in the city centre tomorrow afternoon.