Liberal frontbencher Jonno Duniam will quit politics before the end of the year, in another major blow to the struggling Coalition which is experiencing its lowest levels of popularity in decades.

The Tasmanian senator, who was elected to parliament in 2016 and is considered one of the Liberals’ best talents, said it was an “extremely difficult decision to make” but one he had been considering for “quite some time” to spend more time with family.

“Where we’re at in the polls is irrelevant,” he said on Sunday.

“It wouldn’t matter whether we were on the precipice of a landslide win or the doldrums of electoral defeat, I would be making the same decision I am today.”

Duniam, who serves as the shadow home affairs minister, said he had informed the opposition leader, Angus Taylor, who asked him to finish the Coalition’s immigration policy work before quitting.

The 43-year-old said the party’s leadership change earlier this year was an “exhausting” and “difficult” process that catalysed his decision to retire.

“When the leadership change came along, it started to really wear on me. It was less about direction and more about my personal energy levels, and to that end, that is why I made that decision,” he said.

Duniam said he felt as if he was “letting down the team” but had given 25 years to the party and needed to prioritise family.

“I am leaving the field of battle and leaving them on it, which is not a good feeling, but at the end of the day one has to make a choice,” he said.

“I’ve got three boys, I’ve got a family that I need to ensure have me around as well, and that’s why I made this decision.”

The newly elected Liberal president, Tony Abbott, said he was “very disappointed” but understood how tough public life could be.

Abbott said Duniam’s retirement required the opposition to put “every hand on deck right now to save Australia from a terrible government and keep us our best selves”.

“I hope his replacement is drawn from a very strong field of proven achievers seeking to serve our country and advance the ideals of the Liberal party,” he said.

The home affairs minister, Tony Burke, told Sky News on Sunday Duniam was one of the opposition’s “best and brightest”.

Duniam acknowledged his announcement came at a difficult time for the Coalition, which, according to current polling data, could be wiped out as the opposition at the next federal election if One Nation’s surge in popularity remains.

In May, a Redbridge Group/Accent Research poll published in the Australian Financial Review showed One Nation’s primary vote had surpassed Labor and the Coalition for the first time.

Earlier this week, Tony Pasin, a conservative Liberal from rural South Australia and a shadow minister, suggested his party and One Nation “work hand-in-glove to defeat Labor” by arranging a deal not to run in the same seats.

The suggestion was quickly rejected by Taylor, and Liberal senator James Paterson criticised the suggestion as “premature”.

Duniam said talking about deals with One Nation two years before a federal election was “not relevant”.

“Because if we’re just going to wave the white flag and say that ‘it’s over now, we’ve just got to do deals with others to get across the line’, then we’re not doing our job properly,” he said.