Chief Minister Katy Gallagher says former ACT Opposition leader Zed Seselja should leave the Legislative Assembly as soon as possible after his triumph in the Canberra Liberals Senate preselection at the weekend.
Ms Gallagher called for a "clear exit strategy" on Monday from the Liberals MLA and said Mr Seselja should not continue to draw an MLA's wage while campaigning for the Senate.
But Mr Seselja said he did not have a date for his departure from the Assembly and would stay on as long as he could contribute and as long as new leader Jeremy Hanson wanted him on the Opposition's front bench.
The former Opposition leader defeated incumbent Liberal Senator Gary Humphries 114 votes to 84 in the party's preselection on Saturday.
Ms Gallagher said it was now time for Mr Seselja to move on.
"I think if you look at this from a moral point of view, we've got an MLA who has made a very public and very clear declaration that he doesn't want to be an MLA," she said.
"He doesn't want to be a Member for Brindabella anymore.
"My own view is he shouldn't sit in the Assembly and take up a seat in the Assembly."
The Chief Minister said Mr Seselja should not continue to draw an MLA's wage when his priority was to be elected to the Senate.
"He's said that in every interview, he's going to be door knocking, he's going to be campaigning, he's going to be running grassroots campaign strategies," she said.
"They take time and I don't think it's again fair or reasonable for the people of Canberra to believe that he will be doing that in all the time that he's not an MLA."
But Mr Seselja said he would stay on as long as he could serve the people of Brindabella.
"That's obviously a completely new standard that Katy Gallagher's trying to set," he said.
"For as long as I'm serving the people of Brindabella and doing my job and my leader here wants me to continue to serve on his front bench, then for as long as I can make a contribution I will and I'll work hard in that particular role."
The former Opposition Leader, who said he was staying on the Opposition front bench at Mr Hanson's request, denied that campaigning for the Senate would interfere with his job as an MLA.
"I certainly won't be using any Assembly resources for campaigning," he said.
"What I will be doing is serving the community as an MLA, as people would expect me to, and for as long as I'm here and I can make a contribution I will do that.
"There will be a significant period of time before the election where I will no longer be serving in that capacity."
Mr Seselja said he did not have a date for his exit from the Assembly, but it would be "well before the election" and before the campaign proper began in August.
But Ms Gallagher accused Mr Seselja of waiting for a personally "convenient" time to leave.
"I don't think there's any reason for him to use the excuse that he's got something to contribute here, that his skills can't be matched or met by a new Member for Brindabella coming into the Assembly," she said.