Nearly 850 jobs are at risk after administrators failed to find a buyer or cash to keep the Coryton oil refinery open.

The plant, which supplies 20pc of fuel in London and the South East, was plunged into administration earlier this year by Swiss owner Petroplus.

Administrators PwC said the site would be wound down over the next three months after the challenge of raising the £625m needed to fund the refinery proved too much. There are likely to be a "substantial" number of redundancies among the 500 workforce, PwC said, while around 350 contractors will learn their fate in the next few days.

There are seven other refineries in the UK - at South Killingholme and Lindsey, both in north Lincolnshire; Fawley, near Southampton; Grangemouth, near Falkirk; Stanlow in Cheshire; and Milford Haven and Pembroke, both in Pembrokeshire. The other main supplier for the South East and London is the Exxon Mobil refinery at Fawley.

PwC entered into an arrangement in February which allowed operations to continue at the refinery while various restructuring and sale options were explored.

But the administrator said this was unachievable against a backdrop of an "over-supplied" European refinery market for both buyers and investors.

PwC said it will now consult with both the trade union and the established staff representative group over their future, but it will continue discussions regarding a possible sale during the time it will take to close the plant. It also warned that the closure was likely to have an impact on staff at two other locations - an oil storage site in Teesside and a research and development site in Swansea.

Steven Pearson, joint administrator and partner with PwC, said: "We have worked tirelessly to explore all feasible options for the refinery. We have had contact with over 100 possible investors and purchasers. We have been unable to reach a deal to date. The current financing market is exceptionally difficult - capital is short and expensive."

A spokesman for the Department of Energy and Climate Change said: "It is disappointing that PwC has been unable to find a buyer for Coryton. This is particularly bad news for the workers at Coryton."

But Labour MEP Richard Howitt said his appeal to the government to intervene had "fallen on deaf ears".

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