Plans for affordable homes in the centre of Dorchester for younger people, and the redevelopment of homes for older residents, are both being held up by nitrogen neutrality rules for the Poole Harbour catchment area.

The two projects are among many which have been caught up in new directives that insist on new developments in key catchment areas having to prove they will not add to the amount of nitrogen entering the environment, which can have negative effects on local rivers.

The Mayor of Dorchester, Cllr Alistair Chisholm, one of the trustees for the Dorchester Area Community Land Trust, said the situation is "immensely frustrating."

"It's been six, almost seven years now… that's the reality of trying to bring affordable housing in a town which doesn't have a lot of brownfield sites," he said.

The trust, with the help of Dorchester Town Council, has been planning to build small affordable homes on the site of the old tennis courts in West Walks, opposite Borough Gardens, aimed at under 35s at below open market costs.

The project has been delayed by a series of difficulties, including claims that it would harm the remains of the town's old Roman wall, buried beneath the walks path.

Those problems had been mainly resolved, only for the proposed development to run head-on into the nitrogen neutrality rules which were not in place when the project started.

Similar difficulties have hit proposals to re-develop the nearby residential complex for older people at Nappers House, also in West Walks.

Cllr Molly Rennie, who is involved with the scheme for 14 homes, said they were originally told the nitrogen issue should be resolved by September but have since heard that the issue has been delayed again and is now likely to have to go to the Prime Minister's office for a decision.

Said Cllr Chisholm: "At the end of the day we may be able to suggest methods which would offset the nitrogen, but it's all taking forever."

He said that more recently, another site for affordable homes was identified, in Garfield Avenue, Dorchester, with a request to be considered being made to Dorset Council.

" We didn't even get a response… volunteers are making massive efforts to bring forward affordable housing for the town but it seems there is always a blockage at Dorset Council, not officers, but members and in particular the Cabinet," he said.