London, Sep 9 (IANS): Britain's Prime Minister David Cameron courted controversy after he briefly left his official ministerial red box unattended on the table of a train carriage.

Cameron moved away from his table, leaving the red box behind with the key still in it and with no security cover, the Daily Mirror reported Monday.

A fellow passenger on the train took a photograph of the red box which was published by the newspaper.

"I carried on walking through the train and two carriages on I saw the PM's red briefcase on a table all alone. First of all I couldn't believe that Cameron was on the train unprotected, I just walked past him," the report quoted the passenger as saying.

"I could have quite easily have damaged it or scratched it or run off with it. And above all I couldn't believe the key was in the lock. It was just sitting there. I could probably have run off with it if I'd wanted to. But instead I took a photo," the passenger said.

Criticising the PM for leaving the official case behind, former deputy prime minister John Prescott told the Daily Mail: "I'm staggered that a prime minister should be so slack about looking after government secrets.

"The box could have contained detailed confidential intelligence about Syria. I never let mine out of my sight... The guy needs to get a grip," Prescott said.

Meanwhile, the prime minister's office has denied reports that Cameron breached security by leaving his ministerial box unattended.

"The box was not left unattended. The prime minister’s security detail was there at all times,” the Daily Mirror quoted a 10 Downing Street spokesman as saying Sunday.