Conservative Party infighting over Europe has reached a new level of bitterness as new polls show the Leave side pulling ahead after its best week of the campaign so far.
After 10 days focusing almost exclusively on immigration, the Leave campaign has dramatically reduced the Remain side's poll lead, with some polls now putting the pro-Brexit side ahead.
Former prime minister John Major on Sunday accused fellow Conservatives Boris Johnson and Michael Gove of running a squalid and misleading campaign.
"On the subject that they have veered towards, having lost the economic argument, of immigration, I think their campaign is verging on the squalid," he told the BBC's Andrew Marr.
“I am angry at the way the British people are being misled, this is much more important than a general election, this is going to affect people, their livelihoods, their future, for a very long time to come and if they are given honest, straightforward facts and they decide to leave, then that is the decision the British people take.
“But if they decide to leave on the basis of inaccurate information, inaccurate information known to be inaccurate, then I regard that as deceitful,” he said.
Describing Mr Johnson as a "court jester", Mr Major warned him that, if he won the Conservative leadership after dividing the party over Europe, he could not expect the party to be loyal to him. Mr Johnson and Mr Gove have portrayed themselves in recent days as champions of the National Health Service (NHS), claiming that more funds would be available for the service if Britain stopped paying into the EU budget and blaming EU immigration for hospital waiting lists.
Mr Major said that the NHS would be as safe with Mr Johnson and Mr Gove as "as a pet hamster with a hungry python". But Remain campaigners are worried that the Leave side's arguments about immigration and public services are tapping into a vein of popular anger over the strain on public services that have been starved of cash under the Conservative government.
The Leave campaign is targeting the prime minister's credibility with a new poster saying "You can't trust David Cameron on immigration".
And Ukip leader Nigel Farage on Sunday dubbed the prime minister "Dishonest Dave", accusing him of telling lies to keep Britain in the EU.
Mr Farage was accused of "dog-whistle politics" after he suggested that Britain could see mass sex attacks by immigrants similar to those in Cologne on New Year's Eve if it stays in the EU.
Prominent Leave campaigners, including Mr Gove and treasury minister Andrea Leadsom, distanced themselves from the Ukip leader's remarks, which Labour politicians condemned as disgraceful.
"I can see why the Leave campaign are trying to keep Nigel Farage in a box. It's very lowest-common-denominator politics. I hope Nigel Farage can try and find it in himself to be a little bit more dignified," Labour's deputy leader Tom Watson said.
Mr Farage will represent the Leave side in an ITV forum tomorrow, when he and Mr Cameron will separately face questions from the same studio audience.
Vote Leave, the official pro-Brexit campaign, protested to ITV about the choice of the Ukip leader, who is one of the most polarising figures in British politics.
For its part, the Remain campaign is relishing the prospect of a credibility contest between Mr Cameron and Mr Farage.
Optimists on the Remain side hope that the Leave campaign may be peaking too soon and that, just as a surprise poll lead for independence three weeks before the Scottish referendum turned a harsh spotlight on the Yes campaign, the case for Brexit will come under greater scrutiny as the campaign enters its final fortnight.