Tim Paine has sensationally resigned as Australia's Test captain on the eve of the Ashes after being embroiled in a sexting scandal.

The 36-year-old wicketkeeper made the stunning announcement at a brief press conference on Friday, although he clarified he intends to remain available for selection.

Paine had taken over as Australian skipper from Steve Smith in the wake of the sandpaper scandal during the South Africa Test tour in 2018.

The Tasmanian, who is married with two children, revealed the decision was based on an explicit text exchange with a female former Cricket Tasmania colleague from 2017.

The incident was investigated at the time and Paine had been cleared of breaching Cricket Australia's Code of Conduct but he had recently learned the exchange was set to be made public and subsequently opted to stand down.

"It's an incredibly difficult decision but the right one for me, my family and cricket," Paine said.

"On reflection my actions in 2017 do not meet the standards of an Australian cricket captain or the wider community. I'm deeply sorry for the hurt and pain that I have caused for my wife, my family and the other party.

"I'm sorry for any damage that this does to the reputation of our sport and I believe it's the right decision for me to stand own as captain effectively immediately. I do not want this to become an unwelcome distraction to the team ahead of a huge Ashes series."

Paine became particularly emotional when discussing his role as Test captain, which he described as the "greatest privilege" of his playing career, having led the side which retained the Ashes in England in 2019.

"I've loved my role as captain of the Australian cricket team," he said. "It's been the greatest privilege of my sporting life to lead the Australian men's team.

"I'm grateful for the support of my teammates and proud of what we've been able to achieve together. To them I ask for understanding and forgiveness. To Australian cricket fans, I'm deeply sorry my past behaviour has impacted our game on the eve of the Ashes.

"I've been blessed with a wonderful loving supportive family and it's breaks my heart to know how much I've let them down. They've always stood by me and been my most loyal fans. I'm indebted to them for their support.

"I will remain a committed member of the Australian cricket team and look forward with anticipation for what is a huge Ashes tour."

Paine had earlier this week been included in Australia's 15-man squad for the first two Ashes Tests despite neck surgery in September.

Fast bowler Pat Cummins had been named in that squad as vice-captain, while Smith may be considered to step in as captain having served his penance for his 2018 indiscretion.

The First Test against England is due to commence at the Gabba in Brisbane on December 8.