A man sparked a full scale police operation on Westminster Bridge, after he "abandoned" his car when it broke down.
The bridge was been closed by police and evacuated this afternoon after the car was left in the middle of the bridge.
The white Smart car was left parked in the left hand lane of the bridge, close to the Houses of Parliament.
Police descended upon the bridge at about 3pm to investigate the "suspicious vehicle".
Witnesses posted pictures online showing police cars surrounding the vehicle.
A bomb disposal team later arrived at the scene, and could be seen inspecting the car.
The bridge was closed to the public, and Transport for London tweeted: "A302 Westminster Bridge is closed in both directions due to an emergency services incident, seek alternative route."
The owner later returned to his car, and was escorted to the vehicle by police, who stood down the security operation.
One witness, who wished to be known only as Eugene, told the Standard: "We were walking to Houses of Parliament and passed the white Smart Car parked in a bus lane - it didn't look damaged or in trouble.
"The windows were open and emergency indicators were on.
"A police van was parked some way in front of it and after a few minutes drove closer, blocked the road and started turning traffic and pedestrians back.
"We didn't stick around because my first though was that it could be a bomb and we didn't want to end up in the news as casualties."
Another witness, Michael Denoual, told the Standard: "I work in Westminster and tuned round to a lot of sirens and then saw them, blocking the road.
"They then deployed the robot which looked into the car then about 15 mins later a police officer and another man came walking back over the bridge.
"The police officer then searched car. He then just drove off."
Twitter users were quick to criticise the driver, branding him an "idiot" and a "plonker" for sparking the bomb scare.
One witness, Mahala Mary Clarke, posted on Twitter: "So a bloke parks his car on Westminster Bridge leaves it causing bomb squad police and road closures to walk back to the car like nothing!!"
While Sam Maher said: "New rule: Cars parked on Westminster Bridge get towed away and blown up. No compensation, no apologies."
And Andrew Yee posted: "Westminster Bridge was closed because of suspicious package in car parked in middle of it. Disposal robot turned up. Then stupid driver did."
A spokeswoman for Scotland Yard said the bridge had been closed to the public while an investigation was under way, but refused to comment further.
