The Roads Minister has insisted the M4 motorway in west London is safe for drivers as it reopened a week after it closed for emergency repair.
The road, which is expected to be one of the busiest routes during the Olympic Games, was shut last Friday between junctions 2 and 3 after cracks were discovered on a viaduct.
Mike Penning today said that anyone who argued the bridge was not safe was "scaremongering" and should be ashamed of themselves.
The motorway was reopened to traffic just after 5.30am after engineers completed repairs.
The works to the bridge supports of the Boston Manor Viaduct were due to be completed yesterday.
On a site visit to thank engineers for their work, Mike Penning said: "There is still work to be done but the safe way to open this road was the way we did it this morning.
"I've just passed a message from the Prime Minister to the hard working engineers to thank them for what they have done 24/7 to get this motorway open."
The hairline crack was found on a highly stressed section of bridge supports by engineers who had been carrying out other repairs on the busy section of road.
"We have been monitoring it for years, it was no accident that we found this," the minister said.
"We found the cracks, we were repairing the cracks and when we were nearly finished last Friday we found another crack in a completely different area of the structure. That crack was growing so we shut the road.
"We have repaired it with plating but there is still a lot of work going on and long term we know this bridge will probably have to be replaced."
He said he would offer assurances to motorists that the bridge is safe.
"Don't be scared, scaremongers will be scaring you. Structural engineers have specifically done all the work. No structural engineer in this country is going to say "Minister, you can open that bridge" unless they are certain it is perfectly safe. Anyone saying it isn't safe is scaremongering and they should be ashamed of themselves."
Questioned about the weight limit imposed, preventing trucks weighing more than 7.5 tonnes from crossing, Mr Penning said: "There is a weight limit on it, not for one truck or two trucks. But if it was full of 44-tonne trucks structural engineers say they would have concerns about that.
"If the odd one went across that wouldn't affect the structure but the police would prosecute them."
He denied it was political pressure that prompted the swift reopening of the motorway.
"There was absolutely none at all, structural engineers don't work that way. You can say what you like to them but it's their reputation and their careers, their job is about safety.
"Yes we have a commitment to have this open not only for the Olympics but for the people of London and this country because it's a major route in and out and of course I wanted it open but I said it would open when it was safe and this morning it was safe for seven and a half tonnes."
The M4, which is the main route from London to Heathrow Airport and the West of England, was initially closed between junctions 1 and 3, causing misery for thousands of motorists.
It is expected to be one of the busiest routes during the Games because it links London and the Olympic Park in Stratford with Heathrow.
A Highways Agency spokesman earlier said: "The crack was discovered during an ongoing repair programme.
"Work on that continues and for this reason vehicles weighing 7.5 tonnes or more will still be restricted from using the motorway between the junctions. A diversion route remains in place via the A4 and A312 dual carriageways. Drivers are thanked for their patience during this complex work."
The motorway will officially become part of the Olympic Route Network on Monday, with one lane of each carriageway reserved for competitors, officials and sponsors.
Drivers have been warned the ORN will include temporary changes such as suspended turns, stopping and loading restrictions and traffic signal alterations.