South Africa's media watchdog has ordered the state broadcaster to explain its live broadcast of a speech by President Thabo Mbeki to the ANC.
Mbeki and the ANC are widely expected to repeat their election success
Opposition parties accused South African Broadcasting Corporation (SABC) of becoming a government mouthpiece ahead of elections expected in April.
An official from the media watchdog said SABC had a "case to answer".
SABC has denied bias and says Mr Mbeki's first speech of 2004 had "a lot of news value".
He used Sunday's speech to launch the ANC's election manifesto.
The Independent Communications Authority of South Africa (Icasa) said that SABC had until Friday to formally explain its decision.
Icasa had initially responded to opposition complaints by saying that it could only legally start monitoring election coverage in the three months before the poll date.
SABC spokesman Paul Setsetse said: "This was not an election issue because no election date has been announced."
MANIFESTO MAIN POINTS
$15bn for roads, rail, air transport, telecommunications and energy development
One million jobs to be created in next five years in expanded public works scheme
Promises to improve health services and battle HIV/Aids
More poor households to have electricity, water and phones
150,000 more police on the streets
More border security
Crackdown on corruption
The Democratic Alliance accused the SABC of giving an unfair advantage to the ANC.
The Inkatha Freedom Party said the broadcaster had already "sullied the election process a la Zimbabwe" - a reference to the tight control Zimbabwean President Robert Mugabe has on his country's media.
"The SABC is being turned back into an apartheid-style state broadcaster," the IFP said.
The general elections are widely expected to take place in April, coinciding with the 10th anniversary of the end of apartheid and the move to multi-party democracy.
Most analysts expect Mr Mbeki to be re-elected easily for a second five-year term.