THE Victorian Government has refused to reveal details of the Sunraysia Modernisation Project until a business case for the project is completed.

The National Party and the Victorian Farmers Federation have called on Water Minister Tim Holding to release details of the project and allay fears that it would lead to the expansion of corporate farming in the region.

Mr Holding said the business case for the project was still being developed and any announcements about exactly what projects would form part of the project could not be made until it was completed.

However, Mr Holding said the project, which received $103 million from the Federal Government in July, would see "a pumped irrigation district upgrade of substantial proportions".

"Some preliminary work had been done by Lower Murray Water and the former FMIT in June and we're going to continue to build on that work that will underscore that project," Mr Holding said.

He said the project would bring substantial benefits to the people of Mildura, Merbein and Red Cliffs.

Mr Holding said the funding arrangements were yet to be decided.

"Until we see the business case, it's not clear what the total project cost will be or what it will consist of or what irrigators or the State Government contribution should be," Mr Holding said.

Opposition water spokesman Peter Walsh said the lack of detail was causing concern among irrigators.

"There was the announcement out of COAG and no one knows how that is going to be spent and where," Mr Walsh said.

"The State Government is making grand announcements with no planning."

Mr Walsh said he would be "bitterly disappointed" if the government used the money to expand irrigation instead of upgrading it.

"There's no reason why they can't say a statement that it's for upgrading irrigation and not expanding irrigation," Mr Walsh said.

"If the Minister doesn't release the information then clearly he is very happy to keep fuelling rumours."

VFF Sunraysia president Frank Pedulla said there was talk the project would involve lining channels and pressurising pipes, with a view to expanding the irrigation system, to the detriment of existing irrigators.