Shadow minister for local government Greg Warren has called on minister Shelly Hancock to respond quickly to a council request for help in cushioning the 'rate shock' ahead for Cootamundra farmers.

"Minister Hancock needs to: say exactly when the deadline for harmonisation is; and whether it can be introduced over an extended period," Mr Warren said.

"As it stands, some farmers in Cootamundra are staring down the barrel of an extraordinary rate increase.

"That's a huge hike to absorb and councillors like Cr Charlie Sheahan are rightly concerned."

Mr Warren has written to Ms Hancock saying some farmers were facing rate hikes of more than $10,000, and urging that the demerger process be done "in a timely manner".

Councillor Sheahan, a former Labor candidate for the State seat of Cootamundra, said it was in the best interests of all involved for the minister to speed up the Boundaries Commission review process.

"The council and the majority of the community are really pushing for a demerger, so if that occurred harmonising the rates would be an unnecessary process anyway," Cr Sheahan said.

"This divide among the Cootamundra and Gundagai communities regarding this issue has become bloody ugly. It should be called 'dis-harmonisation' - that would be a far more accurate description of the process. The government's shotgun marriage of Cootamundra and Gundagai has been a disaster from the start and this is just the latest chapter."