The protesters warn specially-designated conservation areas are being destroyed by development or neglect.

Margaret Gilmore reports: "There is nothing legally to stop these sites from being developed"

Those taking part in the lobby insisted a new Wildlife Bill was the only way to protect rare habitats and animals.

They are now encouraging Environment Minister Michael Meacher to bring such legislation alongside the statutory guarantee of open access to four million acres of English and Welsh countryside.

An spokesman for the Royal Society for the Protection of Birds, Phil Rothwell, said: "If the ramblers get a right to roam and we don't get a Wildlife Bill, there will be no birds or wild species for them to look at."

Labour MP David Lepper is backing the campaigners and leading the crusade in the Commons to get further statutory countryside protection.

He has already won the support of 324 other MPs for a Commons motion urging the government to act.

David Lepper: Leading Commons crusade

The destruction of an area designated as a Site of Special Scientific Interest in Mr Lepper's constituency started his interest in the issue.

A farmer started to dig up the Sussex site two years ago, he said.

"It caused a huge outcry and some of my constituents went over there and put back the turf.

"Since then I have learned of many more vulnerable sites across the country."

These are legally protected under the Wildlife and Countryside Act, which was passed in 1981.

The groups that took part in the lobby on Parliament now say it is too weak to stop the threat posed to plants and animals.

A campaigner for Friends of the Earth, Craig Bennett, said: "The government must introduce new wildlife laws urgently.