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

The second largest party in South Africa’s coalition, the business-friendly Democratic Alliance, launched a legal challenge on Thursday to block a 0.5% VAT increase in the country’s new budget, raising concerns that the fragile government could collapse.