ANALYSIS: Saying no to Parliament - What's at stake for Mbete?
While she is yet to give reasons for refusing to return to Parliament as an ordinary member, former parliamentary speaker Baleka Mbete will have a lot to lose if she did.
Her resignation from the most senior role in the National Assembly also comes a day after Deputy President David Mabuza rubbished speculation that he was likely to step down.
He has since requested the postponement of his swearing-in.
On Tuesday, the ANC announced that Malusi Gigaba and Mbete had declined to take up seats in Parliament.
Mbete, following a meeting of the party's national executive committee (NEC), also told journalists she was "bringing her to you". She was referring to Thandi Modise, who the ANC is expected to nominate as speaker during Wednesday's sitting.
The party's former chairperson did not attend Tuesday's ANC caucus meeting - the first since the national elections two weeks ago.
But, while Mbete told ANC secretary general Ace Magashule in a letter that she withdrew her name from the ANC's list to focus on other "political tasks" assigned to her, it's believed her withdrawal has more to do with the lifetime perks she gained for serving as South Africa's deputy president in 2008.
It's understood that if she agreed to be an ordinary MP, she would lose the lifetime benefits she already has from that short tenure.
"Mbete will keep her lifetime pension as a former deputy president as well as the perks, for example, [her] security detail. In terms of the Members of Parliament and Political Office Bearers Pension Scheme Act, as amended, she will forfeit the benefits of deputy president if she accepts a position as Cabinet minister or becomes an ordinary backbencher in Parliament," explained independent legal analyst Phepelaphi Dube.
She said the pension benefits were directly linked to the office Mbete held.
"So if she assumes an office with less money, then her benefits decrease," said Dube.
In 2009, when Jacob Zuma was elected president, Mbete faced the same dilemma when her hopes to remain deputy president failed to materialise. Zuma elected Kgalema Motlanthe to serve as his deputy instead.
Mbete was eventually appointed national speaker, which allowed her keep the benefits.