The number of exposure alerts sent to users of the NHS Covid-19 app in England has risen by more than 60%, according to the latest contact tracing figures, as coronavirus cases continue to rise.

A total of 356,036 alerts were sent to users of the app in England in the week to June 30, telling them they had been in close contact with someone who had tested positive for coronavirus.

This is up from 219,391 the previous week – a jump of 62% – and is the highest weekly figure since data was first published in January and comes as the Government and health officials have suggested self-isolation rules could be adapted to take into account the number of people who have been vaccinated.

The head of the UK Health Security Agency, Dr Jenny Harries, told the Commons Public Accounts Committee on Thursday that work was being done to “tune” the app to work within an increasingly vaccinated population to ensure it was there “for a purpose, not for annoyance”.

Working through what a vaccinated population using the app means is something that we are actively doing at the moment

Ministers have been warned that millions of people could be “pinged” by the app or ordered to self-isolate by Test and Trace, with infections expected to hit around 100,000 cases a day in the summer.

“We have a piece of work ongoing at the moment because it is entirely possible to tune the app to ensure that it is appropriate to the risk,” Dr Harries said.

“When the app came into action, we know it has been hugely successful but it has been utilised in a world where we did not have vaccinations.

“So working through what a vaccinated population using the app means is something that we are actively doing at the moment.”

Earlier, Chancellor Rishi Sunak had acknowledged public “frustration” and said that Health Secretary Sajid Javid is looking at an “appropriate, balanced and proportionate” approach for the app.

Most of England’s remaining lockdown restrictions will end if the Government proceeds with Step 4 on July 19, but changes to self-isolation rules will not come in for another four weeks.

Mr Sunak told Sky News: “I’ve spoken to the Health Secretary about this and he’s aware of the frustration that people have around this.

“I know most people’s concerns rest with how the app is working, and the Health Secretary is aware of that.

“The app counts for the majority of the people who need to isolate, I understand, on the numbers, and he’s looking at what the most appropriate, balanced and proportionate approach to isolation is in these circumstances.”

Labour leader Sir Keir Starmer warned on Wednesday that the plans to end restrictions could lead to a “summer of chaos and confusion”.

He told Prime Minister Boris Johnson that businesses fear “carnage” with the loss of staff to isolation, and people having to cancel social plans.

Some people have suggested they have deleted the app to avoid isolation requests for contacts with Covid-19 infections.

Changes to self-isolation rules in England will not come in until August 16.

Fully vaccinated individuals and under-18s will no longer be told to stay at home if they have come into contact with a coronavirus case but will instead be advised to take a test.

People with confirmed cases of Covid-19 will still be told to self-isolate.