The Democratic Alliance (DA) would never enter into a deal that jeopardised its mandate, the party's leader Helen Zille vowed on Thursday, during a protest on the steps of Parliament.

"When [Deputy President] Cyril Ramaphosa says a deal was done – the DA would never, and has never, and will never, enter into a deal that prevents us from doing our job that the people elected us to do," she told reporters.

Zille, together with DA parliamentary leader Mmusi Maimane and other DA MPs, staged a lunchtime protest in front of the House.

They danced and sang and held up small blue posters, each one posing a parliamentary question that the DA says has gone unanswered by the majority party, the African National Congress (ANC).

The deal referred to is what the presidency has described as an "understanding" reached between political party leaders and Ramaphosa at a meeting in Tuynhuys on Tuesday, after months of tensions in the House reached breaking point last week.

But this blew apart on Wednesday night, after the opposition pushed ahead with a motion accusing President Jacob Zuma of dodging questions over his Nkandla homestead.

Zille said the "deal" had to do with adhering to the rules.

"The deal was very simple. The deal was to stick by the rules. Then President Zuma refused to come to Parliament, therefore breaking the rules. We never gave the ANC carte blanche to break the rules.

"We will not be co-opted into a strategy by the ANC to protect the president from Parliament. Because that is against our mandate," she said.

Thursday's protest focused on the unanswered written questions, and the president's apparent reluctance to appear in the House to answer questions put to him.

Zuma has not returned to the National Assembly to answer questions since August 21 when he was heckled by Economic Freedom Fighters MPs over his Nkandla homestead.

"There are many hundreds of questions that have been asked, for very good reasons, in provincial parliaments across South Africa, and in this National Assembly, that have gone unanswered, or [been] partially answered, or given nonsensical answers.

"And that undermines the very spirit of accountability that is the heart of our Constitution," Zille said.

In the provincial legislatures, there was a "mind-boggling" number of unanswered questions.

"In the Northern Cape, 87% of questions have not been answered. In the Eastern Cape, 45% of questions have simply been ignored," she said.