An "angry" John Major has launched a brutal assault on the "squalid" Brexit campaign being run by Tories Boris Johnson and Michael Gove.
In a furious assault on the Leave campaign, the Conservative former Prime Minister attacked its "deceitful" claims and accused Brexit backers of "misleading" the public.
Taking aim at the former London mayor, Sir John said the "court jester" would not have the loyalty of Conservative MPs if he becomes party leader.
The NHS would be "about as safe" in the hands of Johnson, the Justice Secretary and former Cabinet minister Iain Duncan Smith as a "pet hamster would be with a hungry python", he claimed.
Sir John told BBC One's Andrew Marr Show: "Firstly on the economy and what would happen if we actually left, the Leave campaign have said absolutely nothing to the British people and what they have said about leaving is fundamentally dishonest and it's dishonest about the cost of Europe.
"And 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 added: "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."
Johnson dismissed Sir John's stinging assessment, insisting it was "not true" that the Leave's claims about Britain sending £350 million a week to Brussels was "fictitious" or the campaign was "squalid".
Asked if he believed the attacks against him were part of a plot to "take him out", the former London mayor, told BBC One's Andrew Marr Show: "Whether it is or not, I'm rather with John McDonnell this morning who says that there is too much of this blue-on-blue action and what he wants to hear is the arguments and that's where I am."