Patricia de Lille is expected to take centre stage in the Western Cape High Court on Friday when she takes on the Democratic Alliance (DA), City of Cape Town and Electoral Commission of South Africa over her mayorship.

DA federal council chairperson James Selfe and his deputy Natasha Mazzone said at a briefing on Tuesday that it was a public declaration which De Lille had made during an interview with Radio 702 host Eusebius McKaiser on April 26, that stripped her of her membership of the party.

They based this on a clause in the party's constitution, which states that, if a member publicly declares his or her intention to resign, that person's membership ceases immediately.

Earlier, News24 reported that De Lille rejected an offer by the DA to keep the permanent position of mayor and her seat in the council vacant for the next three months, until the merits for her removal had been argued in court.

De Lille told News24 on Thursday that her lawyers had received an offer which includes that her position will not be "permanently" filled for the next three months, but that an acting mayor will take over while the parties head to court.

Her lawyers subsequently rejected the offer.

Instead, her lawyers are expected to argue that the court should urgently suspend her removal from the DA, and therefore the Cape Town council, and effectively return her to her position, News24 reported. The merits of her removal will then be argued at a later date, while the "status quo" is preserved.

Her team has also requested that the Cape Town City manager be interdicted from informing the Independent Electoral Commission (IEC) that she has ceased to be a member of the DA, and that the IEC also be interdicted from filling the vacancy.

But the DA filed opposing papers on Wednesday in which the party said it was too late as "the horse has bolted".

It said it was open to discussing the merits of De Lille's removal from the party in court "in the next weeks", but not under urgent circumstances on Friday.

Selfe said in papers that the court could not grant De Lille the urgent relief she requested, as she had already been removed from the party.