"We are appalled and find it unacceptable Zille's flimsy excuse of shifting responsibility to the former executive director of the City of Cape Town's Department of Transport, claiming civil servants denied her information," the party said in a statement.
Zille, who is the Premier of the Western Cape, must take responsibility for the escalation of the costs involved in the public transport system from R1.3 billion to R4.1 billion, it said.
"As next year's FIFA World Cup is dependent on among others an efficient transport system in the country, we cannot allow a deliberate derailment of the BRT in Cape Town when similar projects are on course elsewhere in the country."
Zille, in a statement on Sunday, welcomed her role in the project being "put under a very powerful microscope".
"I am happy to be held accountable on the findings of an objective evaluation.
"There is a great deal of documentation on this issue, and a substantial "paper trail"," she said, adding that these would be submitted to relevant enquiries.
"I hope that my role will be investigated fully. That is the best way to establish accountability, not through political point scoring.
"Every single major capital project in South Africa has been subject to massive cost escalation in the past two years," she said, citing Gautrain as an example, the cost of which rose from an initial estimate of R8 million to R25 billion.
Zille attributed the price increases to factors "beyond the control of individuals" such as a hike in the cost of commodities.
"Although cost escalation are a serious problem, they are not the core issue here: the problem is that we were not made aware of
the extent of the cost escalation till a very long time after some managers became aware of them.
"Not having the full facts, made it difficult to take timeous action."
A complete forensic investigation has been conducted, she said, and a disciplinary process had commenced.
"There is a limit to what I can say as the matter is the subject of a disciplinary enquiry. The facts must be evaluated and judged objectively.
"I would prefer to leave things to the conclusion of the forensic audit and the inquiry that will now follow. The ANC has no objective facts and is simply seeking to score political points."
Garrio