Changes to planning rules will make it easier to bring redundant rural buildings back into use.

A relaxation of planning rules will allow the use of outbuildings to be changed under permitted development rights.

Ministers have announced that the proposal will come into force on 30 May.

Rural business leaders have welcomed the changes, but conservationists said it could to uncontrolled building on farmland

The Country Land and Business Association said it had lobbied successive governments for nearly a decade to let redundant buildings to be brought back into use.

CLA President Harry Cotterell said: "Allowing farm buildings of 500m2 or less the flexibility to change into a range of new business uses will help to stimulate rural economic growth.

"It will help underpin farming businesses currently under pressure by creating new jobs and businesses at a time when they are greatly needed in the countryside."

Mr Cotterell said the association was also pleased to see new regulations allowing the change of use of offices into residential properties.

A lack of business tenants meant some owners were paying empty property rates so allowing a change of use would reduce costs and provide much-needed rural homes.

But conservationists called on the government to ensure that the conversion of farm buildings was not abused as they could already be constructed without applying for planning permission.

The suggestion that the government would later in the summer relax controls over converting them into housing was particularly alarming, said the Campaign to Protect Rural England.

There was the danger of unleashing on the countryside a wave of unsightly and intrusive development of farm buildings that could be turned into houses at a later date, said the CPRE.

The organisation said it supported the building of more new housing in the countryside, particularly affordable housing that helped to sustain village communities.

But deregulating the use of agricultural buildings was more likely to lead to sporadic, speculative development, said CPRE senior planning campaigner Paul Miner.

"The government has stepped back somewhat from its original proposals, which would have been damaging to the countryside if introduced.

"But we are alarmed to learn that ministers plan yet more changes to chip away at the planning controls that have effectively protected our countryside from intrusive development for over 50 years.

"This would be a clear break with the Government's own policy to prevent sporadic development in the open countryside."

Mr Miner concluded: 'If agricultural buildings are going to be allowed to change use like any other building, then there should be the same controls over building them in the first place.

"The special pleading of rural landowners for planning exemptions looks increasingly difficult to defend given these proposals."