South Africa's parliament passed the budget's fiscal framework on Wednesday after weeks of political wrangling, but the future of the coalition government was thrown into doubt after a key coalition partner voted against the measure.

The legislation passed by 194 votes to 182, with the biggest party, the African National Congress (ANC), securing the support it needed with the backing of an assortment of smaller coalition partners and parties outside the coalition.

The second-biggest party in the coalition, the pro-business Democratic Alliance (DA), rejected the fiscal framework along with opposition parties uMkhonto we Sizwe (MK) and the Economic Freedom Fighters (EFF), calling into question the DA's future in the coalition.

The budget has been the sternest test of the multi-party government formed by the ANC last year when the former liberation movement of Nelson Mandela lost its parliamentary majority for the first time since apartheid ended in 1994.

Due to be presented in February, it was postponed at the last minute, before a revised version was tabled last month.

Its most contentious elements include proposals to raise value-added tax and not adjust personal income tax brackets for inflation.

The ANC and DA had negotiated for weeks to try to agree to pass the budget together but failed to do so.

The rand has weakened against the dollar and government bond yields risen over recent days as the prospect of a deal between the ANC and DA receded.

The parliamentary speaker earlier rejected calls to postpone Wednesday's vote, after the DA, MK and EFF argued that proceedings at a parliamentary committee on Tuesday to set up the vote were unfair.