The rival camps in Britain's EU membership referendum tore into each other Thursday in an ill-tempered first television debate dominated by accusations of lies and scaremongering.
Former London mayor Boris Johnson and Scottish First Minister Nicola Sturgeon traded barbs in a two-hour, six-way spat fought on the main battlegrounds of immigration and the economy.
The debate ended two hours before the extended deadline to register to vote in the June 23 referendum on whether Britain should stay in the European Union or leave the 28-country bloc.
Brexit campaigners accused the government of trying to rig the referendum and threatened legal action after MPs approved emergency legislation to push back the deadline by 48 hours, due to the registration website crashing on Tuesday due to overwhelming demand.
The move has infuriated the "Leave" camp because many late online requests have been from broadly pro-EU younger voters.
The polls are on a knife-edge with a fortnight to go.
The TV debate, featuring three figures each from the Remain and Leave camps, rapidly descended into a slanging match on assorted facts, and bitter personal attacks.
The Remain camp rounded on chief Leave campaigner Johnson -- with some of the sharpest sniping coming from his fellow Conservative Amber Rudd.
Johnson said Britain had to choose whether "to remain locked in an EU ruled by an unelected elite frankly indifferent to the suffering their policies are causing, or to take back control", as he urged to people to vote for "hope" over "fear".
- 'Con' versus 'nightmare' -
In clashes on EU immigration numbers, Johnson said: "There has got to be democratic consent for the scale of the flows that we are seeing."
In turn Energy Secretary Rudd turned on Johnson, saying: "I fear that the only number Boris is interested in is the one that says Number 10" -- the premier's address in Downing Street.
Should Prime Minister David Cameron fail in his attempt to keep Britain in the EU, Johnson is the bookmakers' favourite to replace him.
Scottish National Party (SNP) leader Sturgeon branded the Leave camp's economic pitch as an "absolute con" while Rudd called their arguments "compete fantasy".
German-born Vote Leave campaign chair Gisela Stuart of the main opposition Labour Party said of the EU: "The noble idea dreamt up in the last century is turning into a nightmare".
"We are shackled onto a failing eurozone which is only getting worse," she told the audience.
Outside the heated television studio debate, would-be voters were taking their last chance to register before the newly-extended deadline.
Arron Banks, co-chairman of the Leave.EU campaign, said it was "a clear attempt to rig the referendum or, at a bare minimum, to load the dice".
"It's a desperate attempt by the establishment to register as many likely Remain voters as possible.
"We are therefore considering all available legal options," he said.
Education minister and Remain supporter Nicky Morgan, said the Leave camp was "turning into a bunch of conspiracy theorists".
- Ex-PMs fire UK warning -
Meanwhile Conservative former prime minister John Major joined forces with Labour ex-PM Tony Blair, who ousted Major in 1997, to warn that leaving the EU would be a "historic mistake".
They warned that "Brexit" could "jeopardise the unity" of the UK by paving the way for another referendum on Scottish independence and threaten Northern Ireland's hard-won truce.
"Although today Northern Ireland is more stable and more prosperous than ever, that stability is poised on carefully constructed foundations," Blair said.
"We are naturally concerned at the prospect of anything that could put those foundations at risk."
The secessionist SNP has said Britain voting to leave the EU, while a majority of Scots voted to stay in, would trigger a second referendum on independence.
However, Sturgeon refused to go into "speculation about what happens in the event of a Brexit vote" when asked directly in the TV debate.
The WhatUKThinks website's average of the last six opinion polls puts the "Remain" camp on 51 percent and the "Leave" campaign on 49 percent, but bookmakers still have "Remain" as strong favourite.
Investors remain wary, and have recently sent yields of government bonds -- seen as a safe haven -- tumbling after buying them up as protection against the political uncertainty.
The yield reached a record low of 1.220 percent at around 0800 GMT compared to 1.253 percent at the close of trading on Wednesday.