Ministers are facing increasing pressure from council leaders and teaching unions to reconsider their plans to open primary schools in England to more pupils from next month.

Calderdale Council in West Yorkshire has joined a number of local authorities in advising its schools against reopening more widely to Reception, Year 1 and Year 6 pupils from June 1 amid safety concerns.

Solihull Council, believed to be one of the first Conservative-led local authorities to question the Government’s proposed start date, has warned that some school places may not be ready for the first week of June.

It came as a poll from teachers’ union NASUWT suggested that only 5% of teachers think it will be safe for more pupils to return to school next month.

In a letter to the Education Secretary, Patrick Roach, general secretary of the NASUWT, said the union remains “unconvinced” that wider reopening of schools from June 1 is “appropriate or practicable”.

The survey, of nearly 29,000 NASUWT members across England, found that around nine in 10 teachers believe that social distancing will be impossible, or will present major issues and a similar proportion are not confident that the proposed measures will protect their health or the health of pupils.

It also found that 87% of teachers believe that PPE is essential to protect staff against the virus.

Dr Roach said: “The results of our survey underscore the fact that the Government has thus far failed to win the trust and confidence of teachers about the safety of reopening schools.

“It is now imperative that the Government takes every available opportunity to provide the necessary assurances that teachers are seeking.”

The union leader called for all the scientific evidence from the Government’s Scientific Advisory Group for Emergencies (Sage) to be made available to teachers and school as soon as possible.

It came as education unions told the PA news agency that they were due to meet Education Secretary Gavin Williamson on Tuesday as part of a weekly conference on the impact of the Covid-19 pandemic on schools.

Last week, Mary Bousted, joint general secretary of the National Education Union (NEU), told teachers not to attend any planning meetings about schools reopening from June 1.

In a Zoom meeting with union officers, held on Thursday, Dr Bousted said: “The timetable is reckless. The timetable is simply not safe, it is not fair, it is not feasible.”

Calderdale Council became the latest Labour-led council in the north of England to advise its schools against a wider reopening from June 1, following similar actions from Bury, Liverpool and Hartlepool.

Sefton Council will suggest schools reopen from June 15 to allow time for an “appropriate risk assessment”, the Merseyside local authority has said.

A number of local authorities in England have acknowledged safety concerns among parents and teachers over the date, but they have not urged all their schools to reject the proposed time frame.

Leaders of Birmingham City Council have sent a letter to parents and school staff saying that they will only support schools opening to more pupils “when it is safe to do so”.

The statement says: “We recognise that for some schools, opening to more pupils safely may not be possible on June 1, while parents and guardians must also feel reassured.”

It adds: “We trust that head teachers will make the right decisions for their school communities.”

Stuart Guest, head teacher at Colebourne Primary School in Birmingham, has told parents that he does not plan to open more widely on June 1 because “the risks are too great”.

In a letter to families, Mr Guest wrote: “We would still be endangering the lives of my staff and the community we serve if we rushed a wider opening.”

John Edmunds, professor of infectious disease modelling at London School of Hygiene and Tropical Medicine, said the decision to reopen primary schools is a political decision but he said it may be that children are less likely to transmit coronavirus to others.

He told the House of Lords science and technology committee: “Clearly the decision to open primary schools or not, is a political one, it’s not a scientific decision. Scientists can offer some advice.

“It looks like the risk to children is low, and that the vast majority don’t have significant symptoms.”

He added: “So the risk to others may be relatively low, but overall you have to weigh up those risks with other things, risks to community, clearly we can’t keep children off school forever, and so on and so forth.

“The actual decision, and weighing all of those things, needs to be done by politicians.”

On Monday, former Labour prime minister Tony Blair said Boris Johnson’s administration was right to start reopening schools as he said some children will have received “no education at all” during closures.

A Department for Education spokeswoman said: “We want children back in schools as soon as possible because being with their teachers and friends is so important for their education and their wellbeing.

“Plans for a cautious, phased return of some year groups from June 1, at the earliest, are based on the best scientific and medical advice. The welfare of children and staff has been at the heart of all decision making.

“We have engaged closely with a range of relevant organisations, including the unions, throughout the past eight weeks, including organising for them to hear directly from the Government’s scientific advisers last Friday, and will continue to do so.”