Australian Deputy Prime Minister Barnaby Joyce apologised on Saturday to Prime Minister Scott Morrison for calling him "a hypocrite and a liar" and said that Morrison had rejected his offer to resign.

Morrison said in a statement that he accepted Joyce's apology.

In a leaked message the deputy prime minister, who heads the junior partner in Morrison's coalition government, said last year that he had never trusted Morrison.

"He is a hypocrite and a liar from my observations and that is over a long time," Joyce wrote to a former staffer of Morrison's Liberal Party who had alleged sexual assault by a fellow staffer.

Joyce's remarks further shake the political position of Morrison, who must call a federal election by May. His approval ratings have fallen over his handling of a Omicron-driven coronavirus outbreak.

"I want to apologise to the prime minister ... I should have never written the text that I did," Joyce told a news conference. "My view from the backbench about the prime minister was based on assumption and commentary, not from a one-on-one working relationship."

Joyce became deputy prime minister in 2021 as the leader of the National Party, not as Morrison's appointee. Joyce's party, which has the power to remove him as its leader, said it would not be commenting beyond Joyce's statement.

Morrison responded, "Relationships change over time. Politicians are human beings too. We all have our frailties and none of us are perfect."

Joyce's text message, first reported on Friday night by Nine Newspapers, was sent through a third party to former Liberal Party staffer Brittany Higgins. She had alleged she was sexually assaulted in Parliament House in March 2019.

The political commotion comes days after a controversy about an alleged exchange between senior Liberal Party members making derogatory remarks about Morrison.

Opposition Labor leader Anthony Albanese said that it was "untenable" for Joyce to continue as deputy prime minister.

"I couldn't care less that the Liberal Party members all don't like each," Albanese said at a briefing. "What I do care about is the consequences of a government that is dysfunctional."

(Reporting by Lidia Kelly in Melbourne; Editing by William Mallard) ((;))