LEGAL action claiming workers on Victoria's north-south water pipeline have trespassed on private property will fail, project authorities say. 

About 50 activists gathered on a farm at Glenburn, north-east of Melbourne, to issue Melbourne Water workers with summonses for alleged trespass, and indicated three other pipeline staff would also be prosecuted.

The protesters say workers are not legally allowed on private property to build the pipeline from the Goulburn River to Melbourne and will fight the project in court.

But project director Rod Clifford said today that he was "very confident" of overcoming court action.

"We have the right to enter private land under section 133 of the Water Act so that we can construct vital projects like this one," he told reporters.

"We recognise that entering private land is a very sensitive issue. That is why we go to great lengths to communicate our rights and obligations with landholders."

Mr Clifford said the company was confident its workers had the right to build on private land and the 450 pipeline staff employed in the field would be fully supported if they faced civil action because of their work.

"The project has not been delayed in any way by the protest today," he said, adding that the pipeline should be largely finished by early next year.

However, a barrister employed by the protesters intends to carry out a citizens' prosecution of the workers.

Legal papers say the workers face charges of wilfully entering as a trespasser, neglect or refusing to leave as a trespasser and trespassing likely to cause breach of the peace.

Protesters say this is a landmark development in their fight against the $750 million project, which will pump 75 gigalitres of water each year to Melbourne.

They will ask a magistrate to immediately stop the project and throw the pipeline workers off private land while the case is heard.

Barrister Serge Petrovich, who is representing the protesters pro bono, is confident they will win and said more summonses would be issued against water authority workers.

"I don't expect us to be unsuccessful, I think we've got a very reasonable prospect of winning this or we wouldn't have brought it, this is not a stunt," he said.

The staff given summonses today are expected to contest the charges in Seymour Magistrates' Court on January 29.

AAP