Countryside without special conservation status should not be included in the proposed South Downs national park, landowners told a public inquiry.

The Country Land and Business Association (CLA), said proposed boundaries contained "new" land not inside the existing areas of outstanding natural beauty.

The landowners' lobby group said a national park comprising only the rolling chalk downland had been the original aim of conservationists.

About 17 per cent of the planned park is not included in the Sussex Downs and East Hampshire areas of outstanding natural beauty, established 40 years ago.

CLA regional surveyor Fenella Collins said: "If these additional areas did not meet the natural beauty criteria in the Sixties, it is unclear why they meet them now."

She said there were already more than 35 million visits a year to the Downs, more than any existing national park, while other national parks had a poor record of encouraging economic and social well being in the areas they covered.

The CLA said the Government and the Countryside Agency had largely ignored the level of private investment in the Downs when the park plan was drawn-up.

The agency said the Downs had been a "live contender" for park status since the Forties.

Jane Cecil, the agency's head of finest countryside, said all the land identified met the natural beauty and recreation criteria, the key requirements for a national park.

She said it would be wrong to confine the status to more rugged areas and none of the existing national parks were near heavily populated South East England.

The inquiry is due to sit until September. The Environment Secretary's final decision is not expected until 2005.