Video report by ITV News Political Correspondent Paul Brand
Boris Johnson has insisted that Brexit can still deliver £350 million a week extra for the NHS as he set out his suggestions for a "glorious" exit.
The Foreign Secretary laid out his vision for Brexit in a 4,000-word article published just six days before Prime Minister Theresa May sets out her official policy on the issue in Florence.
The Foreign Secretary's decision to publicise his own Brexit strategy is likely to fuel speculation his leadership ambitions remain undimmed.
But Mr Johnson insisted on Saturday that he was "all behind" the Prime Minister and "looking forward" to her speech in Italy.
The £350m figure was widely derided during the EU campaign and after the result Mr Johnson and others appeared to distance themselves from it.
However, Mr Johnson repeated the claim in his latest article for the Telegraph newspaper, adding that it would be a "fine thing" if a lot of it went on the health service.
Once we have settled our accounts, we will take back control of roughly £350 million per week.
Critics warned there is "absolutely no chance" of the £350 million pledge being delivered and said Mr Johnson was untrustworthy.
In his article, Mr Johnson also said Britain should not pay for access to European markets and must seize the opportunity to reform the tax system to encourage investment.
Continued membership of the single market and customs union would make a "complete mockery" of the referendum result, he suggests.
The Government should "seize the opportunity" of Brexit to reform our tax system to boost investment, he argued.
"Outside the EU there are obvious opportunities - in agriculture, fisheries, in the setting of indirect taxation," he said.
"At the stroke of a pen, the Chancellor will be able to cut VAT on tampons; often demanded by Parliament but - absurdly - legally impossible to deliver."
Labour's Chuka Umunna, leading supporter of Open Britain, which is campaigning for continued single market membership, said: "No one can trust a word he says."
"The £350 million a week promise was a fib, and there is absolutely no chance of it being delivered. Boris should be apologising for his disgraceful conduct in the referendum, not continually making the same impossible promises.
"He's like an old rocker who sings the same tunes, but they just don't sound right anymore. A period of silence on his part would be welcome."
A spokesman for Labour leader Jeremy Corbyn said the article exposed the divisions in Mrs May's top team.
"In the process he has exposed the Tories' real Brexit agenda- a race-to-the-bottom in regulation and corporate tax cuts to benefit the wealthy few at the expense of the rights of the rest of us," they said.
"The Foreign Secretary even has the gall to dredge up the fantasy of £350 million a week extra for the NHS.
"The Prime Minister must spell out now how this will be paid for, or stand condemned for once again trying to mislead the British public."