The mayor of South Africa's coastal city of Cape Town, Patricia De Lille, has said she will step down amidst a drawn out, acrimonious relationship with her political party, the Democratic Alliance (DA).

She signed her resignation letter on the steps of the Cape Town High Court after filing papers challenging a report which resulted in the DA laying criminal charges against her.

She is alleged to have knowingly covered up fraud involving the city's transport authority.

Ms De Lille denied any wrongdoing saying: "One report cleared me of wrongdoing and the other one found me guilty."

The veteran politician also said that she was resigning from the DA, the main opposition party in South Africa.

“I can no longer stay in this abusive relationship,” she said.

"I have been fighting from a very young age in my life... my fight has never been about personal gain," she added.

Ms De Lille, who has been mayor for the last seven years, told reporters that two more councilors would be resigning in solidarity with her.

Five DA councillors resigned in solidarity with her last week after she delivered her final address to the council.

“I’m free now," she told reporters, adding that she would be taking a two-week break to consult her family, signalling that she might revive her former political party, the Independent Democrats.

Ms De Lille is expected to officially step down on Wednesday at 19:00 local time (17:00 GMT).