Spears has defended driving with her son. Photo credit: X17

"I made a mistake and so it is what it is, I guess," the 24-year-old singer told the US TV show, Access Hollywood.

Spears was pictured driving in traffic with her son Sean on her lap, rather than strapped into a baby car seat.

The singer insisted she was reacting against pursuing photographers. "Being put in the situation that I was in, it was kind of bad with the paparazzi."

X17, the agency who took the photographs, have denied her claims. "These pictures were taken in a very peaceful context, in which photographers exhibited no aggressive behaviour," a statement read.

Kelly Davis, vice president of X17, said only two photographers were involved, one of whom happened to be in the coffee shop car park when Spears arrived.

One photographer

"At the point where she made the decision to drive with the baby in her lap, there was only one photographer and he wasn't even shooting," said Davis.

"They [paparazzi] usually are swarming around her, but on that day they weren't."

Police visited Spears following the publication of photos, to seek information for the Department of Family and Children Services.

Under California law, children are required to be secured in a child-safety seat until they are at least 6 years old or weigh at least 60 pounds (27 kg).

Both the sheriff's department and the California Highway Patrol said they are not investigating the incident.

Spears, who has taken time out from recording since marrying dancer Kevin Federline, gave birth to Sean in September.