The row over more than 100,000 WhatsApp messages concerning the Government’s Covid response deepened on Thursday as Matt Hancock was accused of sending a “menacing” late-night message to the journalist who leaked them.

They also sparked concerns over whether too many key decisions in government during the pandemic were made through WhatApps, and raised fresh questions over the closure of schools, and led to new tensions with teachers.

As the former health secretary faced a wave of new allegations, Isabel Oakeshott claimed he sent her a “threatening” message at 1.20am yesterday as news was breaking of The Daily Telegraph’s publication of his WhatsApps.

Mr Hancock admitted telling Ms Oakeshott she had made “a big mistake” after she passed on his private messages to the newspaper, having helped him to write his Pandemic Diaries memoir. But he denied the message was threatening and accused her of a “massive betrayal and breach of trust”.

He argued: “There is absolutely no public interest case for this huge breach,” stressing that the “material for his book” had already been sent to the official Covid inquiry.

However, she flatly rejected this claim. “He’s making a fool of himself to suggest there’s no public interest in this,” she told Times Radio.

“If Matt Hancock wants to enter into an ugly fight with me, then that would be an interesting judgement on his part, I wouldn’t advise it.”

She appeared to admit she had broken a non-disclosure agreement with Mr Hancock, but defended her conduct.

Ms Oakeshott later fired back again, saying she makes “no apology whatsoever for acting in the national interest”. “The greatest betrayal is of the entire country,” she added.

Amid the war of words:

*  Ministers came under fire over whether blunders were made in the Covid response because so many policies were being shaped on WhatsApp.

*  Mr Hancock and former education secretary Sir Gavin Williamson faced a furious backlash over disparaging comments about teaching unions during the pandemic.

*  There were questions over whether children and other young people were asked to make too many sacrifices to protect the elderly who were more at risk from the virus.

*  According to the WhatApp messages, Mr Hancock clashed behind-the-scenes with Sir Gavin on moves to keep schools open during the Covid pandemic.

*  Schools minister Nick Gibb said it will be up to the Covid-19 inquiry to decide if the Government made the right decisions to shut schools.

*  Baroness Hallett, chairwoman of the inquiry, said there would be “no whitewash”, after Ms Oakeshott suggested there might be. The first evidence hearings are due to start in mid-June.

The leaks also raised concerns over government use of WhatsApp. Tory MP Dr Dan Poulter, an ex-health minister, told Times Radio: “I certainly don’t think WhatsApp is the best way of conducting government discussions. It’s convenient, it’s easy. But when you’re making really big decisions about the country, you need to have proper evidence and a proper evidence base to do that.”

Geoff Barton, General Secretary of the Association of School and College Leaders, told BBC Breakfast: “Crucial issues of public health were being made through WhatsApp exchanges and they don’t resonate with the conversations which we were having with the Secretary of State for Education.”

Schools minister Mr Gibb insisted on LBC Radio: “The actual decision-making that takes place in government takes place in minuted meetings. People have always had private conversations in the voting lobbies, over lunch... so WhatsApp is an extension of that.”

However, the leaks appear to show decisions were being made, or at least communicated by Mr Hancock, by WhatsApp for example on initially not testing people from the community going into care homes at the start of the pandemic. The then-health secretary insists the decision was due to limitations on testing.

England’s Chief Medical Officer Sir Chris Whitty had advised testing of everyone going into care homes but this was prioritised for people coming from hospital as they were deemed more likely to have caught the virus. Mr Hancock messaged that he was fighting a “rearguard action” to prevent a “policy car crash” as Sir Gavin resisted moves to close schools.

In the event, on January 4, after many younger children had returned to classes for a single day, Boris Johnson said schools would close and exams cancelled amid a national lockdown. They did not reopen until March 8.

The messages also show how Mr Hancock and Sir Gavin had earlier expressed exasperation with teaching unions. Mr Hancock messaged Sir Gavin to congratulate him on a decision to delay A-level exams for a few weeks. “Cracking announcement today. What a bunch of absolute arses the teaching unions are,” he wrote.

Sir Gavin responded: “I know they really really do just hate work.”

Sir Gavin said his comments had been “about some unions and not teachers”.

He added: “I have the utmost respect for teachers who work tirelessly to support students.”

But Mr Barton condemned the “contemptible” comments.