The Prime Minister has called the blacklisting of workers by large construction firms "completely unacceptable" ahead of a Labour Opposition Day debate on the issue.
Responding to a question by Labour MP Ian Lavery during Prime Minister's Questions, Mr Cameron said:
The blacklisting that occurred was a completely unacceptable practice. I think the previous government was right to bring in legislation to make it unlawful.
We've seen no evidence the blacklisting regulations introduced are not doing their job and the company responsible was shut down in 2009 ...
I do welcome the openness and frankness that Labour are using an Opposition Day debate to look at something that went wrong while they were in office.
More top news
A Google executive has broken Felix Baumgartner's world record after jumping from the edge of space.
Charlene White explains her decision not to wear a poppy on screen.
Children's pocket money payouts have risen more than twice as fast as their parents' wage increases since the late 80s, research has found.