The appointment of ANC Deputy President Kgalema Motlanthe to the cabinet will create a bloated Presidency with three ministers, two directors-general and a chief operating officer, according to an analyst.
Motlanthe was sworn in on Friday as a second minister in the Presidency.
Currently, the Presidency has Essop Pahad as Minister in the Presidency and Deputy President Phumzile Mlambo-Ngcuka, whose powers are more ministerial than that of an executive deputy president.
Motlanthe will be minister without portfolio in charge of government business, taking over the key role of Mlambo-Ngcuka.
The Presidency is also manned by two directors-general: Frank Chikane and policy unit head Joel Netshitenzhe, who operates at director-general level by virtue of being the former head of the Government Communication and Information System.
The Presidency also has a chief operating officer, Trevor Fowler, and several deputy directors-general and chief directors.
The head of political studies at Wits University, Professor Sheila Meintjies, said it was necessary for Motlanthe to get experience in the government in the remaining days of Thabo Mbeki's administration.
However, Meintjies raised concerns about the growth of the Presidency since Mbeki took over from Nelson Mandela in 1999.
Another problem was that there was no effective ministerial process that allows for co-operative governance between the Presidency and the government departments, the political analyst said.
"One of the difficulties with the Presidency is that it has grown. You have cumbersome activities (in the Presidency). Its functional aspect has not worked in South Africa. That is why we have a problem of service delivery," she said.
"Implementation (of policy) depends on the effectiveness of departments," she added.
Although the Presidency has shortcomings, Meintjies believes Motlanthe will learn more about the dynamics of the executive and its Presidency.
When ANC President Jacob Zuma was the country's deputy president, he gained extensive experience on the inner workings of the government, Meintjies pointed out.
Luthuli House last week forced Mbeki to appoint Motlanthe to manage the transition until next year's general election and to oversee the government's performance.
Motlanthe was jobless when he was elected deputy president of the ANC, after he moved from being a permanent Luthuli House employee as the party's secretary-general.
He was, however, sworn in as a parliamentarian last month. His salary will almost double from around R572 000 a year as an MP to more than R1-million a year as a cabinet minister.
He will be entitled to a driver, a state car, private office and other perks. Motlanthe had previously eschewed what he termed the trappings of power.