Philip Hammond has refused to endorse Theresa May to lead the Conservatives into the next general election.
The Chancellor said the Prime Minister was the "best person" to take the country through Brexit but failed four times to back her in the top job in 2022.
During a visit to Scotland, Mr Hammond also declined to deny reports that he offered to back Boris Johnson for leader after the disastrous snap election.
Mrs May announced she planned to lead the Tories into the next national poll last month but the move was viewed as a gamble that could spur opponents into action.
Speaking to journalists in Dundee, Mr Hammond was pressed four times on whether Mrs May was the best person to lead the party at the next election.
"I'm not going to get into a conversation about the future Conservative Party leadership," he said. "I'm completely behind her, she's making an excellent job of managing the Brexit negotiations. All of us need to focus on delivering a Brexit that works for Britain.
"I think you will see next week at our party conference, the party is unified behind Theresa May delivering us Brexit that works for Britain."
The party is preparing to head to Manchester at the weekend for its autumn conference after weeks of reports of turmoil over Brexit divisions and claims of jockeying for position to succeed Mrs May.
According to reports in The Sunday Times, Mr Hammond texted the Foreign Secretary at 4am the morning after the election to offer his support for a leadership run under a deal where he remained Chancellor.
Asked about the claims, Mr Hammond said: "There was an awful lot of communication going on during the early hours of that morning - texting, telephone calling between all sorts of colleagues.
"I don't recognise some of the material I've seen in the Sunday papers.
"What I do know is the most important conversation I had on that night was with Theresa May when she told me she had decided to seek to form a government and she wanted me to serve in it."