"We will look at the reasons behind our MPs' absence during this important sitting in order to ensure that any disciplinary action is taken on the basis of facts," Sizani said in a statement on Sunday.
"The poor attendance of Members of Parliament from all political parties on this Bill cannot be condoned," he said.
According to parliamentary attendance records, the African National Congress had 171 MPs present in the house on Thursday, he said.
The National Assembly passed the Basic Conditions of Employment Amendment Bill on Thursday, but after heated debate, could not vote on the accompanying Labour Relations Amendment Bill.
Debate on the Bills was dominated by the issues of labour broking and strike balloting, with the opposition objecting strongly to recent changes it sees as concessions to the Congress of SA Trade Unions.
Sizani bemoaned what he called an "irresponsible decision" by the Democratic Alliance to walk out of the process.
He claimed opposition MPs, led by DA Parliamentary leader Lindiwe Mazibuko, gathered in the parliamentary bar and watched the proceedings on a television monitor.
"It is shameful and scandalous that an official opposition would boycott a parliamentary sitting on such a crucial national matter that affects the livelihood of millions of our workers in favour of sitting in a bar," he said.
"The parliamentary leader's role in this disgraceful conduct is a clearest indication yet that this DA caucus is rudderless."
The ANC would propose that the parliamentary bar be closed when the Houses of Parliament were in session, said Sizani.
Mazibuko could not be immediately reached for comment. – Sapa