The National Farmers Union has promised to tackle the Environment Agency after fields were submerged again in the latest floods.

Oxfordshire farmers complained their fields were affected last week because the ditches on their land have not been cleared.

They claim that their fields were sacrificed so that heavily populated urban areas, like London, were not flooded. The Environment Agency denies the claim.

The row stems over the Environment Agency no longer helping farmers clear the ditches because of a reduction in its funding.

The NFU is now preparing evidence for the Pitt Report into last summer's flooding, complaining farmers are unfairly treated. A spokesman said it would lobby Parliament if the report did not push for the agency to help clear farmers' ditches.

Andrew Forsythe, NFU secretary for the Vale and Wallingford branch, said: "I first heard this theory (about London) about three or four years ago. To me, it is logical conclusion.

"The Environment Agency used to do a lot of drainage work in the countryside and on agricultural land.

"But because of policy change and new legislation coming in, the responsibility is now largely down to the farmers.

"The EA stopped doing their bit because of a lack of Government funding, but this change in responsibilty hits farmers at a time when they need help the most in winter.

"With help for proper drainage, they could manage the water very easily in Oxfordshire. They hold the water in the countryside so anything further south is kept safe."

He said crops were being damaged, costing farmers.

But Environment Agency spokesman Hayley Willoughby said the agency had the power to do maintenance, but not the duty.

That fell to the landowner, but the agency used to have more money to do that type of work.

She said: "With a shrinking maintenance budget, we have had to prioritise the work we can do, which means doing maintenance where the risk to property is highest.

"Our theory, under the Catchment Flood Management Plan CFMP, is to use the flood plain of all rivers to hold flood water.

"There has not been any pressure to try and hold water in the rural areas to save London. Taking last week's flood, for example, we got as much water away down the Thames as possible, opening all weirs early and keeping them open so the Thames was running as fast as it could."

She added: "It is a common misconception that we are sacrificing the countryside to save London', but it isn't true."

Bampton arable and dairy farmer John Hook said: "The water can be got away if it is managed properly.

"They can manage the water if they want to. They are flooding us to save the loos in London. Imagine what would happen if they had to go through this down there.

"We expect rain at this time of year, it is natural, but if they want to park their water on our land, they should at least pay for it."