THE Victorian Greens have challenged the Coalition parties to block crucial Government orders giving Melbourne the right to pump water through the controversial north-south pipeline.

"We will put their rhetoric to the test on this," Greens water spokesman Greg Barber said.

The Coalition has 18 Parliamentary sitting days to lodge a disallowance motion in the Upper House against the Government's amendments to the 2009 Eildon-Goulburn Weir bulk entitlement orders.

However, it has so far refused to make any commitment to do so.

The order, signed by Water Minister Tim Holding, allows Melbourne Water to gather, store and take water from Lake Eildon via the controversial north-south pipeline.

Other clauses in the order:

Give Melbourne the right to take the first 75,000 megalitres of water savings from the Government's $1 billion irrigation modernisation works before June next year.

Allows water savings derived from stage one of the Northern Victorian Irrigation Renewal Project to be shared equally between Melbourne, irrigators and the environment.

Simply states water savings from the second stage of the NVIRP will be shared based on "future negotiations with the Commonwealth".

This last clause fails to back commitments from both the Federal and Victorian Governments to ensure second-stage savings are shared equally between irrigators and the environment.

So far Coalition Water spokesman Peter Walsh has made no move to get any of his Upper House colleagues to introduce a disallowance motion, telling The Weekly Times he had no comment on the issue last Friday.

However, on Monday Mr Walsh said he was seeking legal advice on the impacts of disallowing certain clauses in the order or the whole document.

"We have 18 (sitting) days to stand up and give notice that we will disallow," Mr Walsh said. "Then we have another 12 sitting days after that."

The Upper House only has to sit for 30 more days this year, meaning the Coalition could delay introducing a disallowance motion until the end of the year.

The Coalition has tied itself in knots in the past on whether it supports or opposes Melbourne taking water from Goulburn River via the north-south pipeline.

In September last year Coalition urban water spokeswoman Louise Asher stated: "A Coalition government will not take water from that pipeline".

Three days later the Coalition did a backflip stating they would use the pipeline's water "as a last resort" for "critical human needs".