Urgent work to clear ten Oxfordshire landfill sites of polluted water and potentially explosive gases looks likelyto cost the county council £13m.

At four sites, gases are already leaking, and could pose a risk to people living nearby if work does not start this year.

The Government has so far refused to meet the cost of the work and the county council is warning that council tax payers could have to foot the bill.

To meet new Government standards, a seven-metre-deep trench must be built around each site, which will then be filled with clay. Then every site - some occupying more than 40 acres - must be covered with clay. Holes would be drilled to siphon off gases and polluted water.

The cost of clearing the four urgent sites - Stanford-in-the Vale, Alkerton, near Banbury, Milton-under-Wychwood and Oakley Wood, near Wallingford - has been set at £9.5m over six years.

A further £4m is needed to make safe lower priority sites at Littleworth, near Wheatley, Dean Pitt, near Chipping Norton, Eyres Lane, Ewelme, Stratton Audley, Ardley Wood, and Worsham Quarry, near Burford.

Patrick Coulter, head of waste management, said: "I do not think there is a risk to health immediately. But if gas is moving away from sites where there are houses nearby, there is a worry. We know that at one or two sites it is happening.

"But we do not want to worry people unnecessarily. We have talked to residents individually - we are only talking about a handful of homes and a few scattered farmhouses.

"We will be starting work in some areas this year where it cannot be left much longer."

The Government allows the county to borrow £500,000 each year for urgent work, but this will still leave £1m a year for the four key sites, plus another £4m needed to complete the remaining six.

The county council's environment committee next Wednesday will be urged to put pressure on the Government to come up with more money for the work.

Mr Coulter said because the Government wanted the work done, it should pay.

"We are ahead of most local authorities in getting on with work to ensure that our old landfill sites stay safe.

"But this is very expensive and it is not reflected in our budget. Government cash is essential to deal with a problem that is not just in Oxfordshire but nationwide.