A senior Liberal has endorsed Sussan Ley as party leader while reinforcing immigration concerns that prompted rogue MP Andrew Hastie to abandon the front bench.

As one of the party’s few remaining representatives in an outer-urban seat, western Sydney MP Melissa McIntosh said she understood why Hastie decided to quit shadow cabinet to speak more freely about immigration.

The now-former home affairs spokesman announced his resignation late on Friday, saying he felt he wouldn’t be able to uphold cabinet solidarity.

“I can feel that for him because I come from an outer-metro seat where high immigration is putting pressure on infrastructure,” McIntosh, the opposition’s communication spokeswoman, told Sky News on Sunday.

“Infrastructure costs are out of control. Our hospitals are bursting at the seams. Major roads around Western Sydney International Airport have potholes on them still.

“I can see why he has this as an issue. It’s important to his community, it’s important to my community.”

But the Liberal team remained behind Ley, as she seeks to rebuild the party after its May election drubbing, McIntosh said.

“She’s come in at a very tough time,” she said.

“Australians are very disappointed in us, so you can’t expect that when we’re in such a dismal state, from parliamentary terms, that things are always going to be bright and fuzzy, and we’re all having a beautiful time.”

On Saturday, Hastie defended his decision to quit shadow cabinet but ruled out challenging Ley for the leadership, despite publicly airing his future leadership ambitions.

He said he wanted the freedom to be more outspoken on immigration by sitting on the back bench.

Hastie’s outer Perth electorate of Canning is representative of the sprawling mortgage-belt suburbs across Australia’s capital cities where immigration has become a lightning rod for discontent over cost-of-living pressures.

“On the back bench, I’ll continue to advocate for things I believe in,” he said.

One of the former SAS soldier’s closest colleagues, James Paterson, said the opposition needed to resolve big questions about its policy positions as quickly as possible.

“One of the reflections we’ve all had about the last parliamentary term is that there wasn’t enough debate and contest about ideas, that we need to robustly contest policy before we settle on it,” he said.

Hastie’s resignation follows the recent demotion of another hardline campaigner on immigration, Senator Jacinta Nampijinpa Price. She was sacked from the shadow ministry in September after refusing to apologise for comments that singled out Indian Australians.

Paterson described Hastie as a very good friend, adding that he would like both the Western Australian MP and Nampijinpa Price to return to the front bench in due course.

“They are high-quality contributors to our cause and … we are better when we’ve got them on our team contributing,” he said.

Ley said Hastie didn’t raise policy matters when he called her on Friday to inform her of his decision to leave the front bench.

Asked about specifics on Saturday, he refused to get into the details.

The Liberals have not locked in any immigration policies a a major review following their crushing defeat in May continues.

The resignation came just days after Ley wrote to her senior team, outlining policy priorities in their portfolios and her expectations about solidarity.

-AAP