LONDON — Britain’s official pro-Brexit campaign broke the law by overspending and has been referred to the police, regulators said Tuesday, prompting renewed calls for another referendum on any European Union divorce deal.

Vote Leave breached spending rules in the June 2016 vote and has been fined $80,843, the Electoral Commission ruled.

Britain voted 51.9 percent to leave the E.U. against 48.1 percent who voted to remain in the trading bloc, paving the way for the biggest change in the country's trade and foreign policy for decades.

Two years on from that result, the Britain remains intractably divided on what its future relationship with the E.U. should look like, or indeed if Brexit should go ahead at all.

Political maneuvering over the issue has plunged Prime Minister Theresa May’s ruling Conservative government into a series of crises. It narrowly avoided a defeat in the House of Commons late Monday by just three votes.

"Vote Leave" was the official campaign organisation for Brexit. Oli Scarff / AFP - Getty Images file

An attempt by May to unite warring ministers behind a post-Brexit plan, negotiated earlier this month at her Chequers country retreat, collapsed within days after the terms proved unpalatable to lawmakers and grassroots Conservatives. Her government was rocked by several resignations.

Supporters of Brexit say the 2016 referendum result should be respected. The official divorce mechanism has already been triggered and Britain is due to leave the E.U. on March 29, 2019.

However, growing uncertainty at the impact of Brexit on trade and customs arrangements has prompted some lawmakers from across the political spectrum to demand the process be subjected to a second vote or even abandoned altogether.

One of May’s former ministers, Justine Greening, said the Chequers deal was “a fudge I can’t support.”

“The only solution is to take the final Brexit decision out of the hands of deadlocked politicians, away from the backroom deals, and give it back to the people,” she wrote in The Times newspaper Tuesday.

That sentiment was amplified by the revelations about illegal overspending by the Vote Leave campaign.

“Brexit was not only sold on deliberate lies and false promises, but also by breaking electoral law,” said Conservative lawmaker Sarah Wollaston.

Opposition Labour Party lawmaker Chuka Umunna said: “We know Vote Leave lied on a gargantuan scale — we now know they cheated too and it’s official.” He backed a so-called People’s Vote on the final terms of Brexit.

With only 255 days to go until Britain leaves the E.U., Britain has yet to begin substantive negotiations with Brussels on whether it should retain existing partnerships such as a common customs zone or harmonized consumer regulations.

Analysts warned that the political infighting increased the chances of a “disorderly” or "no-deal" Brexit in which Britain dropped out of the E.U. without any replacement trade or customs pact in place. Business groups say that would cause chaos, particularly at borders.

John Wraith, head of UK rates strategy at UBS, said: “Given the risks to all sides, we still see an orderly exit as the most likely out-turn. But the prospects of that outcome have dimmed over recent weeks in our view, while those of more ominous out-turns have increased significantly.”

Tuesday’s announcement by election regulators follows concern that Russian groups used social media accounts to try to influence the 2016 Brexit result.

Facebook said it found only “a minimal amount" of U.K.-related disinformation when it first investigated in 2017, but in January the tech giant said it would re-examine the issue.

Under British electoral law it is the responsibility of campaigners to ensure that an accurate and complete campaign spending return is finished on time.

The Electoral Commission opened an investigation in November 2017 after it found evidence indicating that Vote Leave's referendum spending was 7,449,079.34 pounds (around $9,865,000), exceeding its statutory spending limit of 7 million ($9.3 million).

Bob Posner, Electoral Commission Director of Political Finance, said it found “serious breaches” in transparency in the pro-Brexit campaign.

“Vote Leave has resisted our investigation from the start, including contesting our right as the statutory regulator to open the investigation,” he said.

“It has refused to cooperate, refused our requests to put forward a representative for interview, and forced us to use our legal powers to compel it to provide evidence. Nevertheless, the evidence we have found is clear and substantial.”