Parliament should consider its benefits scheme for ex-Cabinet ministers who become ordinary MPs, as this is probably the reason why some former ministers have bowed out from further service, the Council for the Advancement of the South African Constitution (Casac) says.
Some former ministers who did not make it back to the Cabinet are "probably resigning for financial reasons", said Casac executive secretary Lawson Naidoo.
Naidoo said that, if the ministers were done with serving and wanted to move on to other things, they would have made that clear before the elections.
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AfricaCheck compiled this report on what MPs and Cabinet ministers earn.
'Losing good people among bad apples'
According to AfricaCheck, Cabinet ministers earn R2 401 633 a year - or R200 136 a month.
Senior MPs, such as the chief whip of the majority party, the chief whip of the National Council of Provinces (NCOP) and parliamentary councils to the president and deputy president earn R1 600 467 a year.
The leader of the opposition, the DA's Mmusi Maimane, is also in this group with a monthly salary of R133 372.
Committee chairs earn R1 405 015 a year, or R121 251 per month, and minority party leaders earn R1 309 563 a year or R109 130 a month.
For "regular" MPs, the lowest salary at the Nationial Assembly or NCOP is R1 106 940 a year, or R92 245 a month.
MPs also get allowances, such as accommodation, travelling, communication technology, stationery and travel for dependents, among other perks to help them perform their work.
Naidoo said that it might be a good idea to have a look at the salary differences for Cabinet members who opt to stay on as MPs, since some of them may have valuable inputs to make in committees.
"In the process, we lose some good people among the bad apples."
He said that, politically, they are there to service the interests of the country, whether they are backbenchers or on the executive.
Naidoo said the only MP he could think of who had stayed on after not making the cut for Cabinet - aside from those who stayed on after a mid-term reshuffle - was Kader Asmal.