Tim Paine has stepped down as captain of the Australia Test cricket team less than a month before the Ashes over a sexting exchange with a former colleague.

Paine, 36, had been expected to lead his side in the series against England which starts in Brisbane on 8 December, but made the "incredibly difficult decision" to leave the role.

The wicketkeeper-batsman did not speak about the nature of the messages in his resignation speech, but Cricket Australia's news website referred to it as "revelations of a sexting incident involving a former Cricket Tasmania employee in 2017".

Cricket Australia said it accepted the resignation and would appoint a new captain, but added the Tasmanian would be available for selection for the forthcoming series. Paceman Pat Cummins is the current vice-captain and most likely choice to become the team's new leader.

Speaking to reporters in Hobart, Paine said: "It's an incredibly difficult decision but the right one for me, my family and cricket.

"As a background on my decision, nearly four years ago I was involved in a text exchange with a then colleague.

"At the time, the exchange was the subject of a thorough CA [Cricket Australia] Integrity Unit investigation, throughout which I fully participated in and openly participated in.

"That investigation and a Cricket Tasmania HR investigation at the same time found that there had been no breach of the Cricket Australia code of conduct.

"Although exonerated, I deeply regretted this incident at the time and still do today."

Paine was unexpectedly elevated to become Australia's 46th Test captain after Steve Smith's ban following the infamous ball-tampering scandal in South Africa in 2018.

While the position was thrust upon him, the 36-year-old has drawn mostly praise for his execution of the demanding dual roles of captain and wicketkeeper, especially in Australia's 2019 Ashes triumph in England.