Jennifer Lopez sent her assistant to spy on her husband Marc Anthony.

The 39-year-old 'Get Right' singer - who gave birth to twins Max and Emme in February - allegedly wanted to make sure Anthony didn't stray while he was on tour.

A source told the New York Post newspaper: "She wanted reports back so he didn't cheat on her."

The couple - who have recently been photographed without their wedding rings on - are reportedly selling their Bel Air home where they tied the knot in a surprise ceremony in 2004.

It seems Jennifer isn't the only one spying. Friends claim Marc is constantly checking the star's phone records and wardrobe.

Another source said: "He's very, very controlling of her. The skirts aren't as short. You don't see so much of that booty anymore."

Marc was seen flirting with women in New York and Las Vegas nightclubs last week, reportedly complaining Jennifer was "making me miserable".

Marc's publicist denies the marriage is in trouble, insisting: "They're doing great."