A feasibility study of the government’s plan said there was a risk of a "malicious takeover" of the convoys, putting road users at risk.
Under the scheme, up to three wirelessly connected heavy goods vehicles will move in a platoon, with acceleration and braking controlled by the lead vehicle. The lorries would still be steered by drivers.
The report, commissioned by the Department for Transport, concludes that the system has the potential to reduce accidents and emissions, while improving traffic flow.
But it also outlines 20 risks, including cyber-attack and the potential for drivers in the middle and back vehicles to lose concentration.
Extreme weather conditions could lead to the sensing system keeping the vehicles a set distance apart malfunctioning.
Other cars could enter the convoy by mistake, and the lead lorry could suffer a tyre blow-out.
The scheme is expected to be tried on major roads next year.
Driving in convoy could see the front lorry push air out of the way, making the vehicles more efficient and lowering emissions. But Edmund King, AA president, said the safety of drivers must come first.
He said: "There have been cases of connected and autonomous vehicles and even road signs being hacked. The safety of the drivers is paramount.
"If the platoon is hacked it could put on the brakes or try to make it accelerate."
- DAILY MAIL