The Prime Minister is sticking to his date for schools opening but acknowledged “it may not be possible” for all of them to do so by June 1.

Speaking at the Downing Street press briefing, Boris Johnson said, despite resistance from many councils, the Government planned to push ahead with the opening date.

“We said we would begin with early years’ settings and reception, year one, and year six in primary schools,” he said.

Mr Johnson said: “Today, I can announce it is our intention to go ahead with that as planned on June 1, a week on Monday.

“We then intend from June 15 for secondary schools to provide some contact for year 10 and year 12 students to help them to prepare for exams next year, with up to a quarter of these students in at any point.”

He said the Government was being “deliberately cautious” and that a final decision would be taken next Thursday as part of the formal review into the lockdown measures.

The PM added: “I acknowledge that the June 1 opening may not be possible for all schools but the Government will continue to support and work with the sector so that any schools experiencing difficulties are able to open more widely as soon as possible.”

Liberal Democrat education spokeswoman Layla Moran said: “Despite the concerns, the Prime Minister seems intent on rushing to bring schools back in a bid to distract from his scandal-hit spin doctor-in-chief.

“The concession to give some secondary school children contact with their teachers from June 15 also highlights the failure to push down the R number.

“The public deserve answers.”

Kevin Courtney, joint general secretary of the National Education Union (NEU) said it was still opposed to the June 1 date.

“We once again call on the Government to engage meaningfully with the education unions on these matters,” he said.

“We stand ready to talk to the Government about how our five tests can be met and then how we can then proceed to a safe wider re-opening of schools.”

The Association of Schools and College Leaders (ASCL) said it welcomed the Government’s recognition that not all schools would be able to open in a week’s time.

But Geoff Barton, ASCL’s general secretary said: “(The Government) has not communicated the rationale for its chosen approach well, and it left primary schools with little time to plan and implement safety protocols.”

“It is also worrying that the government’s crucial test, trace, and isolate system is not yet in place and is unproven.”

He added: “It is doubtful that any part of the education sector has ever been asked to do so much in so little time.”

Teachers’ Union NASUWT said the decision to push ahead with the June 1 opening was “at odds” with scientific evidence on transmission.

NASUWT general secretary Dr Patrick Roach said: “The Government has to recognise that it has not won the trust and confidence of the teaching profession.

“Notwithstanding the Government’s assertions, the bottom line is that no teacher or child should be expected to go into schools until it can be demonstrated that it is safe for them to do so.”

Paul Whiteman, general secretary of school leaders’ union NAHT, said: “That the Prime Minister acknowledges that flexibility will not just be possible but will be necessary is to be welcomed.

“We will take the Prime Minister at his word that schools will be allowed to react to their own local situations and will not be forced into opening or penalised if proceeding with appropriate caution.”