Britney Spears is reportedly worried about how her sister's recent actions will affect her career.

The blonde singer's younger sibling Jamie, 23, recently made headlines when a video emerged of her seemingly breaking up a fight with a knife while in a sandwich shop. In the CCTV clip Jamie, who is mother to six-year-old Maddie, can be seen waving a seven-inch bread blade at a group of men before rescuing her friend, whod been hit by a bottle.

While some view it as a heroic move, Britney is apparently fearful of the repercussions.

"Britney respects Jamie for protecting her friend and is relieved she's OK, but worries maybe her sister went too far by waving the knife around," a source told British magazine Closer. "She can't help being scared Jamie's actions will impact her career. She's worked hard to clean up her image and doesn't want to be linked to 'crazy behaviour'."

Britney is a changed woman following her breakdown in 2007, which saw her shave all her hair off and enter rehab. She's now focusing her time on sons Jayden and Sean, who she has with her ex-husband Kevin Federline, and her Las Vegas residency.

She's also found love again with TV producer Charlie Ebersol and is hoping things can continue as normal following Jamie's run-in with trouble.

"Britney's concerned about the incident, but Jamie assured her she was just in an unfortunate scenario and that she has nothing to worry about," the insider added.

And the 33-year-old singer certainly seems in good spirits, often posting cute snaps of her and Charlie and some with her sons on Instagram.