Speaker Baleka Mbete on Monday turned down a request by the Economic Freedom Fighters (EFF) to bring forward the debate on their latest motion of no confidence in President Jacob Zuma as he resists pressure from the ruling African National Congress (ANC) to resign.
"The Speaker has responded in the negative," an opposition source said.
Mbete had scheduled the vote on the motion for the February 22, the day after the government is due to table the national budget for 2018.
But the EFF asked for it to take place earlier after a week of talks between Zuma and Deputy President Cyril Ramaphosa failed to bring the embattled president to resign.
Opposition parties have said the impasse made Ramaphosa, also the ANC president, appear weak.
The ANC was due to hold a special meeting of its National Executive Committee later on Monday to discuss Zuma's fate. The party is understood to be resolved to remove Zuma without the help of an opposition motion.