The government’s food and farming policies were thrown into disarray after it over-estimated England’s farmland by almost 5m hectares (12.5m acres).

The area of agricultural land in England exceeds the land mass of the entire country, according to junior DEFRA minister Hugh Irranca-Davies.

There were approximately 14m ha of farmland in England, he told Parliament on 16 March.

In fact, the entire area of England – including cities such as London, Birmingham and Manchester – encompasses only 13m ha.

Of this, farmland accounts for about 9.3m ha, which means Mr Irranca-Davies over-estimated the farmed area by 50%.

Shadow farm minister Jim Paice said: “It is astonishing that ministers should think there is more agricultural land in England than there is actual land in the country.

“This would be laughable if it didn’t have such serious implications.

“The fact that the minister responsible for land management doesn’t even know the size of the country is alarmingly incompetent and shakes the foundations upon which important policies are based.”

NFU head of policy Andrew Clark described the 14m ha figure as “very odd”.

It had big implications for government policies regarding food security and the country’s potential agricultural productivity, he said.

“It raises serious questions. I have little doubt that the 9.3m ha figure is correct because it is recorded in the annual June census.

“But what I am concerned about are the implications this has for government policy.

“Along with the food security debate, there is an issue where land is flooded or subject to coastal retreat.

“Our argument is that the government should protect the best and most versatile agricultural land. But they don’t appear to know how much land there is.

DEFRA initially claimed Mr Irranca-Davies had used a “different definition” of agricultural land which also included Forestry Commission land and other land without an agricultural holding number.

But it has now admitted making a mistake.

“Very occasionally, incorrect data is inadvertently included in a Parliamentary Question response, but in such circumstances DEFRA takes immediate steps to rectify the mistake and inform the MP concerned.

“In this case, the figure for the total agricultural holdings in England should have read 9.34 million hectares, as published in the 2008 June Agricultural Survey, rather than 14 million hectares.”