Farmers fear being left with millions of sheep because the market for lamb has been wrecked by the foot and mouth epidemic.

The National Farmers Union (NFU) is calling for a rescue deal from the Government, which may involve a mass cull of sheep.

As many as two million lambs are expected to be ready for the market in the next few weeks.

The NFU wants Whitehall to agree a "purchase for destruction" scheme and put some carcasses in storage for release on the market throughout the year. A spokesman said the disease had destroyed the export market for British lamb.

"There is a problem, especially with light-weight lambs - normally they would be exported," he said.

Some supermarkets have agreed to buy lighter weight lambs. Tesco press officer John Church said his firm was promoting sales of lambs weighing between 10 and 14 kilos, which would normally have been sold to Italy, Spain and Greece.

Meanwhile, it emerged today that blood tests on sheep and lambs rounded up off Baildon Moor for a mass cull have so far revealed no trace of foot and mouth.

More than 1,000 animals which had been grazing on the moor and Shipley Glen were slaughtered earlier this month.

Stephen Coates, who has 75 dairy cattle at Low Springs Farm next to Baildon Moor, said: "I'm relieved - we would have been horrified had they been positive."