VICTORIAN Treasurer John Lenders has refused to guarantee the Government will spend the bulk of its $115 million drought assistance scheme this season.

Under the scheme, the Government promised to spend $58 million on a water rate rebate for irrigators that covered up to the first $1000 of irrigators' fixed water charges and half the balance thereafter.

But the Government will not deliver the rebate to irrigators who gain 30 per cent or more of their water allocations by December 1.

Last season the December 1 threshold was set at 40 per cent and in 2006-07 it was set at 50 per cent.

The Opposition asked Mr Lenders last week to guarantee the $58 million would still be spent on irrigator assistance, even if rain boosted allocations to 30 per cent by December.

Opposition Country Victoria spokeswoman Wendy Lovell asked Mr Lenders to guarantee that: "if Victorian irrigators do not qualify for water fee rebates, this $58 million will still be made available to directly benefit irrigators by way of other drought support initiatives?"

Mr Lender said he was not going to start "the business of hypothetically commenting on whether things are happening or are in or out".

"What I will say to Ms Lovell though is I will be leading the cheering if people in the Goulburn system actually get a 30 per cent water allocation," Mr Lenders said. "That will be the best news that we have heard in the Goulburn system for several years."

However, Ms Lovell said the Government's policy left Victorian irrigators under stress and uncertain about their futures.