Britney Spears' boyfriend has reportedly ordered her to change her clothes more.

The singer's habits of wearing the same outfit for several days and rarely washing her hair are said to have infuriated Jason Trewick, who recently refused to go out in public with her until she took off a dirty dress.

A source said: "Britney isn't the type to cover herself in pretty smelling lotions.

"She hates washing her hair, so sometimes it can smell downright sour. She'll sometimes grab an outfit and wear it two or three times in a week.

"Recently she put on a sundress for the third day in a row, but Jason refused to leave the house with her until she put on something else.

"Thankfully she's trying more now because even she knows you couldn't think of a more embarrassing reason for a relationship to break down."

According to pals, Britney - who was recently pictured in the same orange vest twice in the space of a few days - has always taken a lax attitude to her appearance.

The source added to heat magazine: "It's just plain laziness. She was the same when she was married to Kevin Federline."