A secret trial of the £700,000 ‘Amfibus’ was carried out by Stagecoach, yesterday, in a bid to take over the old Renfrew Ferry route, across the Clyde.

The records revealed that ‘Amfibus’ would be able to cross the river only near high tide and it would crash head-on, into the slipways.

The Stagecoach are now looking for a solution to the problem as they bid for the contract to replace the Renfrew Ferry by ‘Amfibus’, last month.

The bus operates like a standard coach on the road but when it takes to water, it is driven by twin water jets at a speed of about 9mph.

“The problem could be solved by a concrete or steel extension to the slipways”, said Steven Stewart, Stagecoach’s spokesman. "This isn't a stumbling block. We are running technical tests, after which any issues will be addressed", he added.