Cameron said he wants to move forward with plans to force large firms to disclose data on the gender pay gap among staff.
The law was changed during the coalition Government to give ministers this power but, so far, it has not been implemented.
Cameron said he would begin a consultation on the measure this week and said it could "cast sunlight on the discrepancies and create the pressure we need for change, driving women's wages up".
The consultation will look at how gender pay gap regulations are designed and what information is published by companies.
Francis Ingham, director general of the PRCA, echoed comments he made last week to PRWeek in a report on the £10,000 pay gap between senior male and female PR practitioners.
He said: "There's a pay gap. And that's something we need to take seriously, and to address. Its presence deters entrants into our industry, and encourages leavers from it.
"We recognise that as the largest PR association in Europe that the response and remedy needs to be proportionate. This is a complex, nuanced problem as we move beyond the general agreement that it simply cannot continue."
Ingham promised a "serious and sustained" consultation with members on the issue.