The Tories will today challenge the government's commitment to the environment, focusing on plans to build a sea port at a nature reserve.

Peter Ainsworth, visits Dibden Bay - the site of a controversial new port terminal and the location of internationally recognised wildlife reserves.

"I am going to highlight the fact that this is the acid test of the government's commitment to sustainable development," he said ahead of the visit.

"Few people dispute the need for greater container capacity in Britain. But the question has to be asked, is this the right place?"

The shadow secretary of state for the environment will meet protesters and the local Tory MP, Dr Julian Lewis to discuss concerns that the government backed proposals for the port development will over-ride protection for conservation sites.

"What is the point of statutory recognition for areas of outstanding environmental value if they can be submerged in massive new development projects?," he will ask.

English Nature is opposing the development by Associated British Ports of deep water quays, together with a rail terminal and port infrastructure to handle nearly one and a half million containers every year.The government's nature conservation advisers believe the development wreck internationally important wildlife sites if the port expansion plan goes ahead.

Rare birds such as Brent geese, oystercatcher, ringed and grey plover, dunlin, curlew and redshank will be at risk, as will lapwing, wigeon and teal.