Another senior member of Sussan Ley’s team has expressed serious reservations about aspects of the hardline migration plan secretly developed in the former Liberal leader’s office, as fresh details emerged about how the policy evolved.

Guardian Australia has confirmed the proposal to ban migration from certain regions in 13 countries was concocted inside Ley’s office after the Bondi terror attack and never went to shadow cabinet for discussion, blindsiding senior Liberals when it was leaked to several media outlets on Monday.

As the new opposition leader, Angus Taylor, sought to immediately distance himself from the proposal on Monday night, Liberal sources speculated the leak was designed to protect Ley from criticisms about a lack of policies and to “wedge” her successor.

Guardian Australia has spoken to more than half a dozen senior Liberal sources to trace how plans for a set of “immigration principles” morphed into a Trump-style border agenda.

On Tuesday, Alex Hawke, a former immigration minister and one of Ley’s most trusted allies, moved to reassure the local Filipino community after the south-east Asian nation was included among the blacklisted countries in the leaked policy.

The proposal – which was part of a wider plan to lower immigration – sought to curb migration from 37 regions under the control of listed terrorist organisations.

The southern Mindanao region of the Philippines, which has been a hotbed of Islamic extremism, was put under the spotlight after two accused Bondi shooters allegedly travelled there in the month prior to the 14 December attack. Federal police believe the two alleged gunmen did not receive training or come into contact with a terror cell while in the Philippines.

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Speaking before the new leader dumped him from shadow cabinet, Hawke said the Philippines should not have been on the list.

“I can’t understand a good reason why the Philippines would be there when many people have come here, worked in our care sector. We need skilled visas from the Philippines to fill hospitals and aged care and lots of very good skills they bring to Australia,” he said.

“I’d say to the Australian Filipino community, in no way does this reflect on them, and you know they are fantastic migrants, and a lot of people in the Coalition know that.”

Hawke confirmed he was consulted about the broader immigration principles but not the banned regions proposal, even though he was a member of shadow cabinet, the Liberal leadership team, a former immigration minister and one of Ley’s closest political confidantes.

After the Coalition resolved the fight over a net zero emissions target in mid-November, Ley immediately shifted focus to immigration to help counter the rise of Pauline Hanson’s One Nation.

By early December, the shadow home affairs minister, Jonno Duniam, and the shadow immigration minister, Paul Scarr, had developed an overarching plan to lower immigration levels that was ready for Ley to unveil.

But the announcement was twice delayed: first to keep the political spotlight on Anika Wells’ travel entitlements controversy and then because of the 14 December terror attack.

Multiple Liberal sources confirmed that in the aftermath of Australia’s worst-ever terror attack, Ley’s office decided unilaterally to expand the policy, which would ultimately result in the proposal for a banned regions list.

What happened over the course of January is contested by senior Liberal sources, who have different recollections about who knew what about the policy as the fight over hate speech laws, the subsequent Coalition split and leadership speculation consumed MPs.

One senior Liberal MP familiar with the policy told Guardian Australia that Ley’s office first proposed the immigration ban on terrorist-controlled areas three weeks after the Bondi terror attack.

Guardian Australia was told Scarr immediately raised concerns with Ley’s office, including concerns over the impact on humanitarian visas, family reunion visas and broader international relations implications. The proposal was sent in the same week that the government’s hate speech bill was being briefed by the department.

Two weeks later, Ley’s office sent out a second draft of the policy with the immigration ban.

It is understood Scarr sent further correspondence to Ley’s office and raised concerns about how One Nation would respond to the policy.

Scarr released a public statement on Monday, and said he “never agreed” to the policy and had “serious concerns” over its contents.

The document was never signed off to go to shadow cabinet, and the new opposition leader did not see the document, which now sits under his desk.

In a statement, Duniam said the plans leaked on Monday were “policy ideas that I haven’t seen, commented on or contributed to”.

“They haven’t been to leadership, shadow cabinet or our party room for any discussion,” he said. “So, frankly these were not part of any policy work I was a part of or that was progressing through our process.”

One MP said the leaks “showed how desperate” Ley’s office was after the former leader was ousted and said it was “very frustrating”.

Another MP told Guardian Australia the leaks were a “defence mechanism” following criticisms Ley had not formulated any policy, and confirmed that they, and several others in the party, had not seen the proposal.

In a pointed message to Taylor as he weighed up whether to adopt Ley’s hardline approach, Hawke said the Coalition must tread carefully when designing immigration policy.

“I think there’s a broad consensus … that we’re going to need to see more control and the restriction of numbers at the moment,” he said.

“But beyond that, I think you’ve got to be very careful how you handle that. Australia is still reliant on the movement of people, the movement of trade in and out of our economy, and we definitely still need highly skilled people to come and work in our economy. Any policy has to be cognisant of that.”