Matt Hancock has denounced what he said was a “massive betrayal and breach of trust” following the leaking of lockdown Whatsapp messages.

The exchanges were published in The Daily Telegraph after he shared them with journalist Isabel Oakeshott, who worked with the former health secretary on his Pandemic Diaries book.

In a lengthy statement, Mr Hancock denied sending a “menacing message” to Ms Oakeshott – a claim she made last night as she defended breaking a Non Disclosure Agreement (NDA) to leak the messages.

The MP 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.

“There is absolutely no public interest case for this huge breach. All the materials for the book have already been made available to the Inquiry, which is the right, and only, place for everything to be considered properly and the right lessons to be learned. As we have seen, releasing them in this way gives a partial, biased account to suit an anti-lockdown agenda.”

Last night, Ms Oakeshott insisted she gave messages to the Telegraph because of the “overwhelming” public interest and it was not about attacking the former health secretary.

She also claimed she received a “menacing message” from Mr Hancock when he found out about what she had done – but Mr Hancock said “this is wrong”.

He said: “Last night, I was accused of sending menacing messages to Isabel. This is also wrong. When I heard confused rumours of a publication late on Tuesday night, I called and messaged Isabel to ask her if she had ‘any clues’ about it, and got no response. When I then saw what she’d done, I messaged to say it was ‘a big mistake’. Nothing more.”

He said he would not be commenting further on any stories “or false allegations that Isabel will make”.

“I will respond to the substance in the appropriate place, at the inquiry, so that we can properly learn all the lessons based on a full and objective understanding of what happened in the pandemic, and why,” he said.

The first story from the tranche of messages broke last night in the Telegraph, alleging the former health secretary had rejected testing advice on care homes and expressed concern it could get in the way of meeting his targets.

The MP strongly denied the “distorted account”, with a spokesman alleging the conversations had been “spun to fit an anti-lockdown agenda”.

Speaking to TalkTV in her first interview since the article was published, Ms Oakeshott – who received the messages from Mr Hancock while working on his memoir with him – said she had signed an NDA and chose to break it “in the public interest” as it could be “a decade” before the official inquiry into COVID reports back.

She said: “The public interest is overwhelming. Whenever you break a big story which is in the national interest… it can be a rocky road, it can be a bumpy ride.

“I know I am going to get a few knocks over this [but] I am prepared to do this because I think the national interest is so utterly compelling.”

The journalist added: “This for me is not a personal thing about Matt Hancock.”