Scott Morrison has swung to the defence of Liberal MP Sussan Ley, who is under pressure in the regional seat of Farrer despite holding it with a 20% margin, but says unravelling the Murray-Darling Basin plan would carry “significant consequences”.

Morrison campaigned in Farrer on Tuesday, despite its nominal safe-seat status, and was egged by a protestor in Albury. At his press conference on the hustings in the neighbouring seat of Indi – a seat the government is hopeful of taking back from an independent after the retirement of Cathy McGowan – the Liberal leader was at pains to praise Ley as “one of the most articulate and passionate spokespeople for rural and regional life in this country”.

Morrison said Ley had the “ear of the prime minister” and the respect of her Coalition colleagues “because she knows how to raise issues and she is a very talented individual”. He said locals could trust her because “they have seen what she’s done”.

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“That is why I think Sussan does present, I think, the obvious choice here. Her record and her plans speak for themselves and I would encourage people across Farrer, including down here in Albury, to give her that support because she will certainly continue to give you great support.”

A local backlash about water allocations is a major issue in the electorate. Independent Kevin Mack, the mayor of Albury, is challenging Ley in the seat, and is currently the bookies’ favourite.

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Morrison was asked, given the local backlash, whether the government would consider reviewing the Murray Darling Basin plan. He didn’t rule that out explicitly but he argued a bipartisan agreement should not be rescinded lightly.

He said in response to Ley bringing a delegation of dairy farmers to Canberra, the government had asked the Australian Competition and Consumer Commission to undertake work including “an assessment of the socioeconomic impact of things as they are currently operating”.

Morrison said he found the meetings with farmers helpful in understanding how the plan was working on the ground. “We have taken further action and we will get that information and then we will take things from there”.

“The Murray-Darling Basin plan, though, is a plan that has bipartisan support. It is a very complicated plan.

“It is by no means perfect but the absence of that plan or the unravelling of that plan would carry with it equally some very significant consequences so I think you proceed carefully in this area.”

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The Nationals leader, Michael McCormack, has already unveiled a new statutory authority for water infrastructure in an effort to contain the bush boilover over water allocations.

McCormack used a speech to the National Press Club last week to unveil a new Northern Australia Infrastructure Facility-style body for dams, with the new body charged with using “the best available science” to examine how large-scale water diversion projects could be established to deliver reliable and cost-effective water to farmers and regional communities.

McCormack recognised there was “a big clamour” to pause the Murray-Darling plan in some parts of regional Australia – a backlash threatening Liberal and National incumbents. But he argued reopening that process would give the Greens “an opportunity to make it even a more environmental document than it already is”.