The leader of the Ulster Unionists, David Trimble, said the ban could have a "potentially fatal impact, on the peace process".

Alistair Graham: "We do not believe we can have a repeat of previous years."

"The Commission has imposed restrictions.... the most significant of which is that the parade is prohibited from proceeding beyond Drumcree parish church or entering that part of the route which includes the entire length of Garvaghy Road," said Alistair Graham, the commission's chairman.

Orangemen will not be allowed to return to Drumcree Church via the Garvaghy road

"Given the absence of any positive move towards accommodation, we cannot see at this stage how a parade could proceed again this year without having a very serious impact on community relationships, both locally and more widely across Northern Ireland."

He told a news conference the ruling "does not imply any erosion of the rights of Orangeman in Portadown".

"It is taken in anticipation of the cumulative adverse effect on the nationalist community, both in Portadown and across Northern Ireland as a whole, of successive parades proceeding in the face of...total opposition."

Flashpoint

In 1996 and 1997 serious violence accompanied the parade, which passes through Portadown, Co Armagh.

Two years ago, the RUC's decision to ban the march from the Garvaghy Road led to a five-day stand-off between Orangemen and the Police.

Troops were called into the Garvaghy Road last July

Eventually the RUC was forced to back down and let the march through because of the violence, not only in Drumcree, but across the province.

The Parades Commission's decision will be a huge test for the Good Friday agreement, and some Orangemen are predicting it could be the end of the peace process.