Scott Morrison has conceded he made a disastrous mistake by trying to stop Western Australia from shutting its border during the COVID pandemic, declaring he now has a “different view” about the actions of then Premier Mark McGowan.

In an interview for a soon to be released book, the former Prime Minister has revealed he was encouraged by WA colleagues Mathias Cormann and Christian Porter Cabinet to support a constitutional challenge to the move.

“It was a massive mistake. But Mathias and Christian advised me to do it,” Mr Morrison is quoted as saying to veteran political journalist and author Paul Kelly.

“(Health Minister) Greg (Hunt) said to exercise caution, but he was a lone voice. At the start there was no pushback from any Western Australians in our cabinet,” he is quoted as saying in an excerpt of the book released to The Australian.

During the first year of the pandemic mining magnate Clive Palmer launched a High Court challenge to Western Australia’s border closure after he was denied entry to the state in May 2020.

Initially Mr Morrison had supported Mr Palmer’s legal action that claimed Premier McGowan’s policy, which lasted 697 days, was in breach of section 92 of the Constitution guaranteeing free movement between states.

A source familiar with government discussions at the time has told The Nightly that Western Australian Ministers including Porter and Cormann were frustrated at the strict quarantine measures they faced each time they flew between Perth and Canberra.

The High Court eventually found in November 2020 that Western Australia’s Emergency Management Act complied with the Constitution, and the state’s directions did not raise any constitutional issue.

Mr Morrison has declared that he now thinks that closing the WA border was a sensible move but blames his initial opposition to the move as being critical to Labor winning four seats in the state at the 2022 federal election.

“I knew within a short time it was a disaster. I went to work with Mark (McGowan) to fix it. I can’t blame the Labor Party for using that against me. I mean, why wouldn’t they? And I don’t hold it against Mark either. So yes, it was a disaster. I don’t think we would have lost as many seats in WA as we did.”

“I have a different view now. In the first few weeks and months of the pandemic we didn’t really talk about borders,” he said. “We had closed the international border, but what did that mean internally?

“We didn’t give that enough thought because, ultimately, I think the West Australian border made a lot of sense. It didn’t disrupt the national economy. The border was in a remote area. The borders between Victoria and NSW and between NSW and Queensland were a completely different issue.”

His former Assistant Minister Ben Morton, who was also a senior Liberal figure from WA, is quoted as saying the Morrison government’s actions were highly damaging to its political standing in his home state.

“The impression left was that the prime minister was saying that Western Australia had got it wrong. The people were never going to accept that. I went to work to get the decision reversed but it was too late. The issue was being presented as Palmer versus the entire state with Morrison on Palmer’s side.”

During a 2021 television interview Mr Morrison further alienated West Australians when discussing COVID vaccination rates by declaring it was “absurd” for any state to think they could protect themselves from the Delta strain forever.

“Now it’s like that movie The Croods,” he said during an appearance on The Today Show, in reference to the children’s film about cavemen.

“Some wanted to stay in the cave and the young girl wanted to deal with the challenges of living in a different world. Covid is a different world ... we can’t stay in the cave.

Just months before the 2022 election Mr Morrison and McGowan appeared in public at an event in the marginal seat of Swan, to jointly announce a $100 million deal for Edith Cowan University.

“We are both leaders of governments that have much to do and for a long time now … the best way to do that is to work together,” Mr Morrison said at the time.

“And I mean, in Western Australia, I think we have a lot of commonality on the importance of having a strong economy which supports everything else.

“It’s about Federal Labor, it’s not about State Labor, and there’s quite a bit in common I’ve found working with the WA State Government when it comes to how we manage the economy.”

The former WA Premier has not responded to requests for comment on Mr Morrison’s Mea culpa, but the Nightly understands the two men have remained in contact following their time in politics.

The Nightly has also approached former Attorney General Christian Porter for comment on whether he had urged his former leader to fight WA’s border closure. Federal Labor figures said the latest comments by Scott Morrison highlighted that Federal Liberal Party MPs had “failed to stand up” for their home state during the COVID pandemic.