A mother suffered a "horrendous" 30-minute ordeal after a man posing as a police officer stole her car and drove off with her four-month-old baby inside before returning and dumping him on the street, police said today.

Detectives said the 24-year-old woman was sitting in her car in Bolton yesterday evening when a man wearing a police jacket approached and told her he needed her vehicle.

Believing him to be a genuine officer, she started to get out of the car when the man grabbed her arm and pulled her out of the way.

The woman managed to get her two-year-old son out of the back of the car, but the offender drove off before she could get to her baby boy.

The stolen car, a Lexus, was then involved in a hit-and-run crash about 15 minutes later, police said.

Then, about 30 minutes after the theft, a Nissan Micra pulled up at the spot where the carjacking had taken place and a man put the child seat with the baby inside on the pavement near to where his frantic parents were standing. He drove off again.

"This was a horrendous ordeal for the family who were left absolutely distraught that their baby was taken from them," said Detective Constable Graham Clare.

"Fortunately he was returned safe and well but the time he was missing must have felt like an eternity for his parents."

Shortly after the incident, police said the Micra was involved in another collision. A 39-year-old man was arrested on suspicion of kidnapping and theft and is in hospital receiving treatment for leg and neck injuries.