Paparazzi fell for the oldest con game in the books – bait-and-switch!

Cameras flashed, tape rolled as a horde of paps jostled to get a saleable shot of Jamie Lynn Spears with new baby in tow at LAX yesterday.

One prob though for the photogs —  La Chiquita no es Jamie!

Meanwhile the real Jamie Lynn and her baby were led safely through another door undetected and spirited away.

LAPD say they were not escorting the look-a-like as it’s against regulations.

Sgt. Jim Holcomb of the LA airport fuzz explained "All (the officers) did was follow the crowd down to the baggage area.

"The people they were following assumed that this was Spears because she was blonde."

Holcomb said the Spears family requested an escort as Britney was allegedly coming to meet her young sis and niece.

But the person they escorted was just another LA woman in a city of bouncy blonde bobbleheads.

An internal investigation is under way.