Boris Johnson has been urged to block an EU rule which could see drivers forced to buy insurance for vehicles used on private land.
Under plans drawn up by the European Court of Justice (ECJ), people at the wheel of tractors, golf buggies and lawnmowers could face prosecution if they fail to purchase accident cover.
The Prime Minister has previously indicated that the laws will not apply to the UK after Brexit.
But, according to The Telegraph, campaigners fear that the Withdrawal Agreement will mean some ECJ rulings remain in place - leading to an adoption of the punitive insurance measures.
Dominic Clayden, chief executive of the Motor Insurers' Bureau (MIB), said: "Through this application of EU law in Britain, millions of new uninsured vehicles have potentially been created.
“This will end up penalising ordinary people just going about their business every day on private land.
"The users of vehicles like quad bikes, golf carts, tractors and even large lawnmowers could face prosecution for driving without insurance on their own property.”
It follows a High Court ruling, following the ECJ judgment, in which a walker sued a farmer who left him paralysed after running him over in an uninsured 4x4.
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The Court of Appeal upheld the verdict last year and the Supreme Court denied the MIB permission to appeal earlier this month.
Following the Supreme Court’s decision, Mr Clayden warned that the new rules could lead to “a PPI-style claims bonanza”.
He also said insured car drivers on the roads will have to “pick up the tab” as their premiums are sent soaring by the amount of claims.
"Leaving the EU means we now have an opportunity to decide our laws for ourselves in this country, and we want to work with Government to find a path forward,” he added.
“We need a common sense insurance system that works for Britain and is decided here."
Yahoo News UK has contacted the Department for Transport for comment.