Emphasizing the benefits of leaving the EU, Johnson repeated a highly contested claim from the referendum campaign that Britain could use some funds now sent to Brussels to pay for its state-run health service.
But Richard Tice, co-chairman of the pro-Brexit Leave Means Leave group, welcomed the "optimistic vision" set out by Mr Johnson.
In a major speech, the Foreign Secretary will brand having to comply with Brussels diktats as "undemocratic" and "intolerable".
"I believe that would be a disastrous mistake that would lead to permanent and ineradicable feelings of betrayal", he said.
But he also acknowledged European Union "idealism", insisted Brexit was "not un-British" and stressed the possible economic opportunities of leaving, saying: "It's not about shutting ourselves off, it's about going global".
McGrory, executive campaigner of Open Britain, said this seems a further example of division between Johnson and his cabinet colleagues, adding that "the clock is ticking and I'm not even sure the Government knows" what its position is. "There is no sensible reason why we should not be able to retire to Spain, as indeed we did long before Spain joined the European Union, or anywhere else".
He also used his speech to reject the notion that Brexit would result in Britain becoming more insular.
Mr Johnson also repeated his call for another crossing for the English Channel.
"I want to show you today that Brexit need not be nationalist but can be internationalist", he said.
"I absolutely refuse to accept the suggestion that it is some unBritish spasm of bad manners", he said.More news: Philippines opposes China naming undersea features
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"It's not some great V-sign from the cliffs of Dover, it is the expression of legitimate and natural desire to self govern of the people, by the people, for the people".
His keynote speech in London will also been seen as a warning to Theresa May not to give in to pro-Brussels Cabinet ministers.
Two other leading Brexiteers in the cabinet, worldwide trade secretary Liam Fox and Brexit secretary David Davis, will also deliver speeches over the next two weeks.
FILE - Britain's Prime Minister Theresa May walks out of 10 Downing Street in London, Jan. 30, 2018.
It was billed as a Valentine's Day letter to remainers.
Critics have long warned that one of the red lines for the EU in any trade negotiations is that the United Kingdom agrees to "continued adherence to... the Union's legislation and policies, in, among others, the field of the environment, climate change, the fight against tax evasion and avoidance, fair competition, trade and social rights, especially safeguards against social dumping".
However, Leo Varadkar said in that case Ireland would seek to trigger the backstop agreement negotiated in December, which would involve putting in place a unique arrangement for trade between the Republic and Northern Ireland.
But she is caught between warring factions within her Cabinet, half of whom want to remain closely aligned to the European Union to limit the economic shock of leaving, and the other half who want to take advantage of potential free trade deals elsewhere in the world.
"It is only by taking back control of our regulatory framework and our tariff schedules that we can do these deals, and exploit the changes in the world economy", he will say, according to the Telegraph.
"Personally, I would like to stay in the single market", he added during a visit to Paris that year.