"I have always fought for a better deal for Canberra, and for policies that would have real and positive impacts on the lives on Canberrans," Mr Seselja wrote to supporters following Tuesday's electoral commission confirmation of his defeat.

He said "rolling over to the left" would have been "ultimately futile" for the party's prospects of regaining government in the ACT, while claiming federally the party would quickly be restored under new Liberal leader Peter Dutton who belongs to the same faction of the party as Mr Seselja.

After the loss of the only seat held by a federal Liberal in the ACT to the senator-elect David Pocock, Mr Seselja said it was premature to write off the Liberals in the capital and it had an important role standing up to dominant Labor and its ACT government coalition partner the Greens.

In the letter to supporters, Mr Seselja said losing government and the ACT Senate seat "is a bitter blow", but "in politics, things change very quickly" and the party's fortunes would be quickly restored under new Liberal leader Peter Dutton.

"People will write off the Liberal Party as they did in 2007, but we will be back here in the ACT and nationally," he said.

The former senator was most known for his conservative views, but told supporters he also fought for liberal principles in his time in public life and was proud to fight for both, including the centrality of family, freedom of speech, religion, association and enterprise.

While the successful ACT candidates in the recent federal election campaigned for the right of territories to debate voluntary assisted dying legislation, Mr Seselja said he stood for the sanctity of human life.

"There are some who argue that I should have abandoned some of these values as a way to win more votes," he said.

"These critics ignore the fact that at this election those in my party in similar seats who had very different views to mine nonetheless suffered much larger swings than what occurred in the ACT."

He said moving to the Canberra Liberals left would be "both wrong in principle and ultimately futile electorally" in the ACT.

"It's not always easy to stand up to the Labor/Green left in Canberra but it's important that there is a political movement which does."

After a nine-year career in the Senate, serving as a minister in both the Turnbull and Morrison governments, most recently as Minister for International Development and the Pacific, and almost nine years in the ACT Assembly, five as opposition leader, he had many things to say about his achievements in office.

"It was a great honour to be the first federal Liberal representative from Canberra to serve in the ministry," he said.

"I am proud of the impact the Coalition has had on delivering for not only our nation, but also delivering far more investment in Canberra than any previous Commonwealth government since self-government."

On his own future, he hinted at life beyond another political role, perhaps in some other way of serving the community and described the journey with his family as an adventure together following the end of their journey in politics.