The PM said the he had no plans to legislate, although he hinted ministers would not stand in the way of MPs attempting to introduce a backbench Bill.
Meanwhile, Home Secretary Theresa May echoed Culture Secretary Maria Miller earlier this week in suggesting a more limited reduction to 20 weeks.
More top news
More than 200 guns were handed in to police during a regional gun amnesty this month.
Simon's Blog - Sunrises & Sunsets
Wednesday night's weather for the west of the region