The Australian Conservation Foundation has warned the Morrison government will make itself vulnerable to a legal challenge if it rushes remaining approvals for the Adani coal mine before the election, or if the decision maker, the environment minister, has been subjected to political interference.

On Monday the treasurer, Josh Frydenberg, was peppered with questions about the Coalition’s support for the controversial Queensland coal project, and the government’s lack of action on climate change, during a solo appearance on the ABC’s Q&A program.

Frydenberg’s appearance comes as a UComms poll in the treasurer’s seat of Kooyong, commissioned by the activist group GetUp, obtained by Guardian Australia, suggests he faces a tough fight to hold the blue ribbon seat, with 64% of respondents saying they would be more likely to vote for a candidate with a plan to tackle climate change by replacing coal with clean energy.

While single seat polls can be unreliable, the survey of 821 Kooyong residents taken on 28 March has Frydenberg level pegging with the Labor candidate in the seat, Jana Stewart, on the two-party-preferred measure, with Stewart polling 20%, the Greens candidate Julian Burnside on 17% and the climate change-focused independent Oliver Yates on 10%.

Liberals are bracing for an outstanding groundwater approval for Adani to be ticked this week, despite the fact an approval would cause problems in metropolitan contests in the southern states, with the Adani project now a proxy for climate action in the minds of many voters, and a rallying point for third-party activism.

Labor warns government not to make Adani coalmine decisions before election Read more

In order to inoculate themselves from a backlash, federal Liberals in tough city battles have been telling their constituents the final arbiter of the Adani project is the Queensland Labor government, which is still considering a number of outstanding approvals.

Frydenberg said on Monday night it was up to the environment minister, Melissa Price, whether or not to provide the outstanding groundwater approval for the project in the remaining days before the federal election, and he insisted that her decision would be “competent” and grounded in scientific advice.

Price has faced internal pressure from Liberals and Nationals in Queensland to deliver the required sign-off before the government moves into caretaker mode, with reports in the Courier Mail the Liberal senator James McGrath threatened to publicly call for Price’s resignation “if she did not fix a problem she created by attempting a deliberate go-slow on the [Adani] project”.

The ACF’s stop Adani campaigner, Christian Slattery, said the government’s behaviour increased the risk any approvals would be subject to a legal challenge. “The ACF has always looked closely at our legal options at every stage of the approval process for Adani’s coal mine,” he told Guardian Australia.

“The political interference revealed this week raises serious doubts about the probity of this government’s approval process for Adani’s mine. If the minister has been pressured by her Queensland colleagues to abuse the approvals process and rush through a decision before the election, that would make it vulnerable to legal challenge.

This message was backed by the Greens environment spokeswoman, Sarah Hanson-Young.

“The split within the Liberal National party on Adani could expose the government to a legal challenge”.

“Queensland senators are falling all over themselves to divide the government on this dodgy project. Now if environment minister Melissa Price makes a decision, regardless of whether she approves it or not, it could be open to challenge.

“So desperate are these Queensland senators to have Adani signed, sealed and delivered before the election that they might have risked taking the right away from their government to do so.”

Frydenberg was asked on Monday night whether he was happy to “tell the baristas of Batman” that the Queensland coalmine was a good project. The treasurer side-stepped the question. “I’m happy to say we’ll be guided by the science and whatever decision the minister takes, I will support that decision”.

Asked whether he wanted the project to proceed, Frydenberg said the government had taken the decision to support the Adani mine, and Australia needed “strong jobs growth”.

Adani coalmine: Morrison and Frydenberg play down remaining approvals Read more

The treasurer also faced questions from the audience and from his host about electric vehicles, given Frydenberg has previously supported an increased uptake and Scott Morrison has, in recent days, claimed Bill Shorten has declared “war on the weekend” by pursuing a vehicle emissions standard that will result in more EVs in Australia’s vehicle fleet.

The program host, Tony Jones, read back a column Frydenberg had written in support of electric vehicles when he was environment and energy minister, and asked him to reconcile his enthusiasm with the prime minister’s negative commentary since the release of Labor’s climate policy last week.

The treasurer said there was a difference in the approach of the major parties, because “Bill Shorten has these mandated CO2 targets” – which was an approach the Coalition considered during Malcolm Turnbull’s prime ministership, before dumping the idea because of lobbying from interest groups and trenchant opposition from the National party.

Frydenberg said the government was now interested in managing the transition by working and coordinating between jurisdictions “so that if you want to charge your car in New South Wales it is not a different plug and type”.

Asked whether voters should believe what Frydenberg had said – that Australians would be the beneficiaries of a global revolution in electric vehicles – or what the prime minister had said, that having more electric cars in the fleet is a “war on weekends”, Frydenberg dead batted.

“You would like to contextualise it like that,” the treasurer told his host.

“That’s what it looks like,” Jones said in reply.

The treasurer also faced questions about the government’s record on climate change. A 16-year-old audience member professed herself “fed up with you and your party’s inability to take meaningful action” and pressed Frydenberg about lacking a plan to retire coal plants.

“We’ve seen 10 coal-fired power stations close in the last five to eight years,” the treasurer said in response. “So the grid is changing.” He said the transition the questioner referred to was under way “but it has to be managed in the best interests of all Australians”.