Pop star Paulina Rubio filed an emergency motion in Miami, Florida last month (Dec12) to strip her estranged husband of his custody rights.

The Mexican singer wed Nicolas Vallejo-Nagera in 2007, but the marriage broke down in 2011, and the former couple has been embroiled in a bitter custody battle over son Nicolas.

Rubio recently filed legal papers in a bid to have Vallejo-Nagera stripped of his rights to care for the two year old, and in the documents, the star revealed she had hired a private investigator to track her estranged partner.

She claims the private eye found Vallejo-Nagera had "repeatedly demonstrated detrimental behaviour and a lack of parental responsibility."

It is alleged Vallejo-Nagera failed to change one of the tot's diapers and smoked around him, and Rubio has accused her ex of showing a "total disregard" for their son, according to Tmz.com.

According to the documents, Vallejo-Nagera has agreed to have a nanny on hand when he is looking after the youngster.