Britney Spears has again sparked concern her marriage to Kevin Federline is in trouble, after she was photographed shopping without her wedding ring on.

The TOXIC singer was indulging in a bit of retail therapy in Malibu, California, on Saturday (14JAN06), when she was spotted not wearing the ring in pictures published in British tabloid newspapers today (16JAN06).

An onlooker says, "Britney didn't look very happy as she shopped for flowers and was chatting away on her phone."

In recent weeks, family members have laughed off reports suggesting the couple are on the verge of splitting up.