South Africa’s fragile unity government has been shaken again. The country’s second-largest political party broke with partners Wednesday and voted against a national budget.

South African opposition party the Economic Freedom Fighters has written to the speaker of parliament seeking to block lawmakers from meeting on Wednesday to vote on the next stage of the budget process.

South Africa’s coalition government is on the brink of collapse after a leading party broke ranks and voted against the Finance Minister’s budget, forcing the long-ruling African National Congress to rely on smaller parties for support.