Mr Coe will hand in his resignation in March, abruptly ending his 12-year career in the ACT Legislative Assembly.

His departure will trigger a countback of votes in the Gungahlin-based electorate of Yerrabi, which will likely see his former Liberal colleague James Milligan returned to parliament.

A fortnight after leading the Liberals to their sixth-straight election defeat on October 17, Mr Coe had declared his intention to remain in the Legislative Assembly for the next four years and play a "significant part" in new leader Elizabeth Lee's team.

But fewer than three months on, the 37-year-old has changed his mind, declaring its "time for a change for me and it's time for a change for the party".

In an exclusive interview with The Canberra Times, Mr Coe said election defeats "really do take the wind out of your sails", with the October loss compounding a sense of regret and frustration which had lingered in the wake of the Canberra Liberals' failure to win government in 2008, 2012 and 2016.

Mr Coe was the target of criticism and ridicule in the post-mortem of the 2020 election, with his lack of personal appeal, conservative values and stunt-laden campaign all cited as reasons for the Liberals' defeat.

"The election result was tough and the aftermath has been tough as well - there is no denying that," he said.

"As I regularly said, nobody gets into politics to be in opposition. You run to win and you run to govern.

"It is a regret that I never served in a Liberal government. I'm sure that is going to be a frustration that I live with for the rest of my life."

A realisation that he could no longer commit to maintaining the "pace I've set in the past 12 years" confirmed to him that it was the right time to leave politics.

"To be a member of the Assembly or a member of parliament and to do it properly requires a significant commitment and a massive sacrifice," he said.

"It's the right thing to do for me and my family to make this change.

"I just don't think I would be doing the right thing by myself, or my party or the electors of Canberra to do anything other than go at full speed. I just don't think I'm in a position to do that, so to that end the best thing that I can do is to make way for somebody else."

A career politician who has spent almost a third of life in the Legislative Assembly, Mr Coe said he doesn't have his next job lined up, noting there are "no obvious stepping stones from politics."

He has no intention of running for political office in the future, but the father-of-two will remain a member of the party he joined as a 16-year-old.

"Not being involved in the Liberal party would be very difficult for me," he said.

His departure will be a blow for the Liberals on a number of fronts as it rebuilds in the wake of another election loss.

The Liberals' leading vote-winner on October 17, the loss of Mr Coe in Yerrabi will rob the party of its edge over Labor in Canberra's northern suburbs.

Mr Coe has long been one of the opposition's strongest performers in the chamber and committee rooms.

But the resignation of the Liberals' most senior conservative figure in the Legislative Assembly will present their new leader, a moderate, with another opportunity to recast the image of a party perceived as too right wing and out of step with mainstream Canberra.

Mr Coe said he was optimistic about the Liberals' chances of finally toppling Labor and the Greens in 2024 under Ms Lee's leadership.

"She's a good communicator, she's sincere and compassionate," he said. "I think the more that people get to know Lee, more people will like her and respect her."

Mr Coe will stay on until budget estimates wraps up on March 5, when he will formally hand in his resignation to Speaker Joy Burch.

With one of his final messages to the public as an elected representative, Mr Coe urged Canberrans to "demand excellence" from their government.

"We're blessed to live in a city with wonderful resources and wonderful people, but we've got to make sure it's a city that is genuinely accessible for everyone and that we don't exclude people by virtue of cost of living or any other factor," he said.