Britney Spears' parenting skills have come under question once again after she exposed her young son to second-hand smoke.

The pop star was photographed with her two-year-old son Sean Preston on Sunday as he attempted to play with his mom's cigarettes.

Spears is seen in the photos standing in a bikini next to Sean Preston as she lights up. The curious toddler holds a lighter in one hand and reaches for a pack of his mother's Marlboros with the other.

Taken from the Toxic star's Beverly Hills, California home, Spears is snapped reaching down for the pack to stop her curious son taking them.

Spears and her ex-husband Kevin Federline settled their ongoing custody dispute concerning their two young sons - Sean Preston and Jayden James, one - on Thursday, following a bitter 18-month battle.

Under the agreement, which is currently awaiting approval from a judge, Federline retains sole custody of the boys while Spears maintained her allotted two visits and one overnight stay each week.

Studies have proven links between second-hand smoke and childhood illnesses, including ear infections, bronchitis, asthma and other respiratory ailments.