[Adam Cheeseman]

Years of nature protection could be put on hold or reversed if proposed cuts of 15-30% to the budget for conserving England's most beautiful places and wildlife are pushed through in the next few weeks.

Proposals seen by the Guardian show that the Department of the Environment, Food and Rural Affairs (Defra) is proposing to slash the budget of Natural England, its statutory independent nature advisers.

The organisation was set up one year ago by Defra to protect wildlife, maintain nature reserves, and improve the state of Britain's most important natural places.

It is understood that Natural England's £51m budget for new conservation work would be reduced by 15% this year with deeper cuts expected later. The organisation is also being forced by the Treasury to repay the £16m spent setting it up and to meet 2% across the board efficiency cuts

One option being considered by Defra is to cut:

• £4m from improving Britain's most important sites of sites of special scientific interest (SSSIs). These are already in poor condition and the government is certain to not fulfil its election pledges if it cuts the budget;
• £2m making access to the countryside easier for ethnic minorities and others. This is considered vital to make the countryside accessible to all;
• £2m to improve and maintain areas designated as being of "outstanding natural beauty";
• £2m to enhance national nature reserves. These are in danger of being neglected;
• £700,000 on scientific research.

In addition, programmes to conserve the habitats of some Britain's most endangered "flagship" species would be cancelled. These might include the dormouse, the stone curlew, the otter, rare orchids and other birds and mammals.

If the cuts go ahead it could set back conservation many years, say environmentalists.

"When money gets tight, it's always the environment and biodiversity in particular that suffers. Natural England was set up by this government and now it looks as if it is being strangled," said Mark Avery, the director of conservation at the RSPB.

"It would seriously undermine protection of the most important and cherished places and wildlife in England just at the time when the value of the environment is being recognised for the benefits it brings to health and the economy", said a government source.

Natural England has a nominal budget of more than £450m but this is almost entirely ringfenced with payments to farmers and landowners. Any cuts imposed by Defra would have to have to come from the £51m the organisation has to spend on new work.

Defra itself has been given a below-inflation increase of 1.4% in its £3.8bn budget over the next three years as part of the Treasury's comprehensive spending review. But more than £200m of this increase has been earmarked for improved flood defences after this year wet weather, and much of the rest has been set aside to help councils recycle more waste to meet EU targets.

The department has also had to pick up the unexpected costs of the latest foot and mouth and blue tongue disease outbreaks and has not fully recovered from the £200m cuts imposed by the Treasury last year following late farm payments.

"No final decisions on the corporate spending review budget allocation have yet been made. Protecting and enhancing the environment of course remains an absolutely key priority for Defra," a spokeswoman for the department said yesterday.