The Brexit battle took an increasingly bitter turn as MPs prepared to vote on allowing a 48 hour extension to the deadline to register for the landmark poll.
Emergency legislation was being rushed through Parliament after the official website crashed, leaving tens of thousands of would-be voters in limbo.
Downing Street insisted the action was legal, despite some in the Leave camp claiming it was an attempt to try to ensure more Remain supporters got on the voting rolls in time for the June 23 showdown.
The move came as Chancellor George Osborne accused fellow senior Tories Boris Johnson and Justice Secretary Michael Gove of being hijacked by Ukip leader Nigel Farage.
Mr Osborne warned the referendum was now a "battle for Britain's soul" as he launched a personalised onslaught on Mr Farage and what he branded his "disgusting scare stories" regarding migrants.
Both camps claimed backing boosts, as in a coup for the Remain campaign, Tory MP and Commons Health Select Committee chairwoman, Sarah Wollaston quit the Leave side because of the Brexit camp's claim withdrawal would hand the NHS an extra £350 million a week.
"For someone like me who has long campaigned for open and honest data in public life I could not have set foot on a battle bus that has at the heart of its campaign a figure that I know to be untrue.
"If you're in a position where you can't hand out a Vote Leave leaflet, you can't be campaigning for that organisation," Dr Wollaston told the BBC.
A Vote Leave spokesman said: "Sarah's decision is bizarre but we wish her well. Given her views on the EU in the past it is disappointing to suddenly see her repeating lines straight from the Remain campaign hymn sheet."
However, the Leave side heralded a letter from JCB chairman Lord Bamford to his 6,000 workers explaining why he was supporting Brexit.
The Chancellor said the Brexit camp was attempting to create fear of immigrants through a scare agenda: "Disgusting things being said about the bodies of migrants being washed up on the shores of Kent, or about women being raped by migrants.
"Let's be clear this is a battle for the soul of our country. I do not want Nigel Farage's vision of Britain. It is mean, it is divisive, it is not who we are as a country.
"Sadly, Nigel Farage and his vision of Britain has taken over the Leave campaign. And we are fighting against that."
The Leave side seized on comments by Mr Osborne in which he insisted that Turkey would not join the EU as they demanded to know if this represented a change in the Government's stance.
Mr Osborne said: "British Government policy is that it should not join the European Union today. And it is a million miles away from joining. Is it going to be a member of the European Union? No, It's not."
A Vote Leave spokeswoman said: "The Government must now urgently clarify whether its policy on Turkey has changed. Is it now promising to veto Turkish membership?"
Mr Osborne compared the economic impact of the referendum to a game of snakes and ladders, insisting Brexit would be like sliding down a "big snake".
Defending the Government against accusations it is running a scare campaign against Brexit, Mr Osborne said: "There is a lot to be scared of."
Meanwhile, Tory former Cabinet minister Sir John Nott has suspended his party membership in protest at the "tirade of fear" tone of David Cameron's Remain campaign, the Daily Telegraph reports.
And the Remain campaign's tactics have been compared to those of Nazi propaganda chief Josef Goebbels by the founder of Ukip, Professor Alan Sked.