A pro-Brexit group in Britain's referendum on whether to leave the European Union may have broken electoral rules by overspending during the campaign, according to a legal opinion published by a parliamentary committee.
The Vote Leave group may have incurred spending worth £625,000 (NZ$1.2 million) that was not declared to electoral authorities, the opinion said on Friday.
"We consider that there is a prima facie case that... electoral offences were committed by Vote Leave in the EU referendum campaign," the legal opinion published by the Digital, Culture, Media and Sport Committee said.
"These require urgent investigation so that consideration can be given to whether to refer the case to the Crown Prosecution Service for a decision on whether to prosecute," the opinion added.
The Vote Leave group also used Cambridge Analytica, the controversial company at the centre of the Facebook privacy scandal.
Reuters / Newshub.