The national broadcaster wants the State Security Agency to track down employees who leak information.
The SABC board resolved at a special meeting on October 9 that the services of the SSA should be called on to "manage leaks".
It also wanted the spy agency to help the ailing broadcaster in exposing those responsible for leaking sensitive information to the public and media.
However, the plan has been widely condemned by labour and freedom-of-expression groups which say it is "dangerous and illegal" and will further erode trust in the SABC.
They said none of the information leaked in the past had been classified, and had instead exposed alleged wrongdoing.
Minutes from the board meeting, seen by the Sunday Times, reveal that the proposal was made by SABC board member Mary Papayya.
Papayya is acting chair of the media freedom committee of the South African National Editors Forum (Sanef), which has lambasted the plan. Sanef said "the threats to freedom of expression are obvious".
Papayya declined to comment on the possible conflict of interest.
According to the minutes, the previous board also used the SSA to manage leaks.
"The issue regarding the leaking of sensitive information to the public and the media was raised as a concern as it had negative impact on revenue and the reputation of the board," the minutes read.
"It was agreed that the chairperson [Bongumusa Makhathini] be mandated to approach the SSA to provide assistance in managing leaks and identify the loopholes."
The board suggested the process include staff vetting and monitoring "as there were various people who interacted with board information".
It also resolved that a previous legal opinion, that journalists be excluded from any vetting, be circulated to the board.
However there was no resolution that the board would abide by this legal opinion.
SABC spokesperson Mmoni Seapolelo confirmed that the broadcaster worked closely with SSA.
The issue regarding the leaking of sensitive information to the public and the media was raised as a concern as it had negative impact on revenue and the reputation of the board
— Minutes of the SABC board
"The SABC has been declared a national key point. This requires the organisation to engage with SSA on a number of key issues within the ambit of the law," Seapolelo said, adding that the SABC "is not in any way engaging SSA to vet journalists".
SSA spokesperson Mava Scott said the agency could not discuss operational matters.
Communications ministerial spokesperson Zandi Ngubeni said the matter was an operational one and that "the minister [Stella Ndabeni-Abrahams] has not been advised of this investigation by the SABC".
The Sunday Times understands the board's plan was sparked by the leaking of the board minutes earlier this year. These had dealt with complaints that the board's deputy chair, Mamodupi Mohlala-Mulaudzi, and board member Marcia Socikwa allegedly interfered in the work of management. Both denied the claim.
The board also wanted to know who had leaked the SABC's strategic plan and debt information, the Special Investigating Unit's investigation of and disciplinary cases against a number of former and current senior managers, and the probe into the R185m security tender allegedly awarded irregularly by the corporation's interim board.
The director of the Helen Suzman Foundation, Francis Antonie, called the SABC board's decision "dangerous and illegal", saying it might further erode the public trust in the broadcaster.
"They have no business doing this and we will continuously monitor [the process] if they succeed in spying on their staff." Antonie said none of the information leaked had been classified, and it had exposed alleged wrongdoing.
The president of the Broadcast Electronic Media and Allied Workers Union, Hannes du Buisson, said his union would challenge in court the board's "shocking and criminal" decision to "spy" on its members.
The general secretary of the Media Workers Association of SA, Tuwani Gumani, said the intention of the board showed that the SABC "hasn't changed since apartheid".
In June, the SABC was on the brink of collapse, warning that it could be forced to go off the air unless the government came to its rescue. The broadcaster, which remains the only source of news and commentary for millions of South Africans, this year requested a R3.2bn government guarantee to stay afloat. It has so far received R2.1bn.
Labour law expert Tanya Mulligan said it would be a violation of SABC staff members' right to privacy if the SSA agreed to the request to monitor staff.
"If they agree with the SABC board, they will be abusing their powers."
In September, the North Gauteng High Court in Pretoria declared a number of sections of SA's interception law unconstitutional.
The court found that - in the absence of a law authorising it - bulk surveillance and the interception of foreign signals were unlawful and invalid, Mulligan said.
Civil society Right2Know also condemned the board's decision.
"They must then answer what it is that they are hiding," Right2Know spokesperson Thami Nkosi said.
"This board is using the same tactics used by the previous board to intimidate its staff," said Nkosi.
Sanef has strongly condemned the SABC board's plan.
Sanef's Kate Skinner said: "We are well aware of the chilling effect of security agents probing journalists working at a public broadcaster. There is simply too much scope for abuse. The threats to freedom of expression are obvious." She called on the SABC board to urgently reconsider its decision, which she said was "dangerous, unacceptable and unconstitutional".
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