The writer who handed more than 100,000 of the former health secretary Matt Hancock’s messages to a newspaper has defended her actions, saying she was acting in the national interest.

Isabel Oakeshott, who is at the centre of a row about the leak of Hancock’s correspondence to the Daily Telegraph, hit back after his criticism of her actions.

“The greatest betrayal is of the entire country,” she said, in a statement responding to Hancock’s accusation that she had betrayed his trust.

Oakeshott added: “Hard though it may be for him to believe, this isn’t about Matt Hancock, or indeed any other individual politician. Nor is it about me.”

Along with the Telegraph, Oakeshott – a longtime critic of public health measures taken by the government during the Covid pandemic – has sought to portray the leaked messages as evidence some lockdown curbs were unnecessary.

On Thursday, she said: “We were all let down by the response to the pandemic and repeated unnecessary lockdowns. Children, in particular, paid a terrible price. Anyone who questioned an approach we now know was fatally flawed was utterly vilified; including highly respected and eminent public health experts, doctors and scientists.

“So, far from being protected, the NHS may never recover, as millions of patients condemned to year-long waiting lists are discovering. Meanwhile, the economy is in smithereens.

“It is now essential that the public inquiry, set up almost two years ago, quickly establishes deadlines for its work and answers the urgent question about whether lockdown, with all its impacts, was proportionate. These issues must be addressed well before the next general election.

“Against this backdrop, the Telegraph exposé is clearly in the overwhelming public interest. The outpouring of support I and the paper have had from ordinary people who suffered – and are still suffering – the consequences of the mistakes we are exposing shows how desperately the nation wants answers.

“I make no apology whatsoever for acting in the national interest: the worst betrayal of all would be to cover up these truths.”

The latest Telegraph article based on the messages originally handed to Oakeshott by Hancock so she could ghost-write his pandemic memoir featured Boris Johnson’s concerns that he might be accused of having “blinked too soon” in declaring a second lockdown in winter 2020, as Covid deaths rose sharply.

It included one exchange in which Johnson cited concerns from a UK scientist that the modelling for the number of deaths could be wrong. After Simon Case, the cabinet secretary, provided the latest death statistics, Johnson noted that those for England had fallen marginally, adding: “The attack is going to be that we blinked too soon.”

In other messages showing government discussions about Covid policy during the pandemic, two of Johnson’s media advisers, Lee Cain and James Slack, warned in June 2020 against an early lifting of some restrictions as being potentially “too far ahead of public opinion”.

Oakeshott’s statement came after Hancock said he was the victim of a “massive betrayal and breach of trust” over the disclosure of the messages.

The former health secretary also apologised for the impact their release had on those he worked with during the pandemic.

Hancock gave the messages to Oakeshott as they collaborated on his memoirs. She subsequently handed them to the Telegraph, which published a series of stories based on the correspondence with fellow ministers and officials.

Oakeshott has faced questions about why she ghost-wrote a book for Hancock that put across his version of the government’s response to the pandemic while she had in hand the WhatsApp messages she now claims tell a different story. She has said she wrote the book he wanted, that there was too much material to go through at the time and that, after she finished writing Hancock’s book for him, her responsibility then became to the public.

Hancock has said: “I am hugely disappointed and sad at the massive betrayal and breach of trust by Isabel Oakeshott.

“I am also sorry for the impact on the very many people – political colleagues, civil servants and friends – who worked hard with me to get through the pandemic and save lives.”

He said there was “absolutely no public interest case for this huge breach” because all the material used for his book, Pandemic Diaries, was given to the Covid-19 public inquiry.