But Mrs May insisted this morning that the cabinet ARE united behind her - despite weeks of splits and outspoken comments.
Rather, than address the specific case, Ms May simply said: "I've accepted, Andrew, that there have been problems with the rollout".
The PM denied that calling the snap vote was a mistake - even though she went on to lose her majority.
The jockeying for Mrs May's job has added more uncertainty to Brexit negotiations.
His latest intervention will revive fears in No 10 that Mr Johnson may storm out of the Government and position himself as a "Brexit martyr". The only surefire thing mentioned in her speech is that the Brexit will happen on March 2019, but the proposed two-year transitional period afterwards displeased her supporters who thought that it was too long while simultaneously upsetting her critics who thought that it wasn't long enough.
Secretary Johnson also said Britain must not pay for access to the EU's single market.
On Brexit, Mrs May said European Union leaders had welcomed her Florence speech, adding that while London is preparing the ground for leaving the European Union without a deal, she hopes and expects to be able to reach a good settlement in Brussels.
The words "strong and stable" were conspicuous by their absence in Theresa May's speech ahead of the Conservative Party Conference, which gets under way in Manchester tomorrow. May knows she will need to win their support if her party is to stand a chance in the next general election, which must be held by 2022.
And the amount graduates must earn before they start student loan repayments will be raised from £21,000 to £25,000, a saving of £360 next year for graduates earning above the new threshold.
'That's why we will invest an extra £10 billion in our Help to Buy: Equity Loan scheme to help a whole new generation of young people, across the United Kingdom, with the upfront costs of home ownership.
The Government also plans a £10bn expansion of the Help To Buy scheme, which is aimed at helping an extra 135,000 people get a foot on the housing ladder.
"Making progress as a nation means supporting young people and families to achieve their dreams of home ownership", Chancellor of the Exchequer Philip Hammond said.
The failure of her campaign severely undermined her authority, but Mrs May insisted in an interview with The Sunday Telegraph newspaper that she will stay on as leader to fight the next election.