It is understood Theresa May and some in the intelligence community had worries about Mr Johnson’s ability to keep information confidential.
Sources close to Mr Johnson said he had access to everything he needed to see.
Asked whether information had ever been held back from him, the Tory leadership frontrunner said this was “not true”.
Pressed about the matter at a Conservative leadership hustings in Darlington, Mr Johnson said he would not comment further on national security issues but he was “extremely dubious about the provenance” of the reports.
His leadership rival and current Foreign Secretary Jeremy Hunt also refused to comment, telling the hustings: “We have the finest intelligence services in the world in this country, but that does depend on some discretion by the foreign secretary.”
A Number 10 spokesperson said it did not comment on intelligence matters, but that Theresa May trusted Mr Johnson in the role.
They said: “It’s a matter of fact it was the PM’s own decision to appoint Boris Johnson as foreign secretary, in full knowledge of all the responsibilities that that job involves.”
On 20 October 2016, Mr Johnson paid his first visit as foreign secretary to MI6’s headquarters at Vauxhall Cross in London.
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After he was shown around by Alex Younger, the chief of MI6, Mr Johnson addressed staff and held an informal question and answer session.
“I was delighted to welcome the foreign secretary to our Vauxhall Cross headquarters so he could see first-hand the kind of work that MI6 does,” the chief, known as “C”, said at the time.
Mr Johnson was effusive in his praise.
“Even from my relatively short period as foreign secretary I can testify to how vital the work they do is,” he said.
It is understood that Theresa May and some in the intelligence community had worries about Boris Johnson’s ability to keep information confidential.
And the tension went back as far as the time when he was Mayor of London and she was home secretary, when one source claims he angered her by inadvertently revealing confidential information before it was due to be made public.
Once he was in government, on occasion Downing Street would even convene smaller meetings, or “pre-meets”, to discuss sensitive subjects rather than include him as foreign secretary, a senior figure has told me.
One of his allies confides “it was obvious there were concerns on issues from early on” and suggests “there was a constant question of whether he was really seeing everything” – the full intelligence picture that he would be entitled to in his role as foreign secretary.
It’s said that he worried constantly about being cut out. But, this is not just about the keeping of secrets, but Theresa May’s desire to keep political control.
It’s suggested that the real issue was a lack of trust and hostility between Mr Johnson and Theresa May. One source believes Mr Johnson was excluded from seeing some sensitive information because there was a hostile relationship between him and Downing Street, not because of reservations from the intelligence services.
And they suggest that despite early doubts among the security services about him, they eased over time and by the time he left his post, they had good relations.But behind the scenes a row had been taking place about whether Mr Johnson would have access to all the intelligence produced by the UK’s spies, according to a number of sources, who spoke anonymously because of the sensitivity of the subject.