Sadiq Khan has warned of his rising concerns over the “pingdemic” disrupting London’s “absolutely crucial” public transport, food supplies and bin collection services.

The Mayor’s intervention on Thursday came as the “pinging” crisis grew with Boris Johnson being urged to hold a meeting of Whitehall’s Cobra emergency committee to consider deploying the Army if necessary as a “last resort” to ensure supermarket shelves are not left empty in the coming weeks.

Mr Khan called on the Government to examine bringing forward from August 16 changes to the guidance so that double-jabbed essential workers do not have to self-isolate if they are “pinged” by the NHS Covid-19 contact-tracing app.

New NHS figures revealed a record 618,903 alerts were sent to users of the app in England and Wales in the week to July 14, telling them they had been in close contact with someone who had tested positive for coronavirus.

The Mayor told the Evening Standard: “I am increasingly concerned about our ability to maintain current levels of absolutely crucial services like public transport, food supplies and bin collections.”

Later he told LBC Radio: “We are talking to the Government about whether they are able to extend the exemption scheme so those key workers across our city — not just Transport for London but police, fire, food supplies — if they have had both jabs and they have had a negative test, if they can continue working.”

In other developments:

* The Government was rushing out a list of sectors for which the self-isolation rules would be relaxed, although Business Secretary Kwasi Kwarteng said it would be “very narrow”.

* Supermarkets urged customers not to panic buy in response to reports of emptying shelves for some ranges such as fresh produce in some stores, saying they are continuing to receive regular deliveries. Mr Kwarteng said he did not “recognise” reports of widespread shortages. But Iceland boss Richard Walker said the Government should be “panicking” to resolve the crisis which has seen more than 500,000 people “pinged” in just a week.

* After the closure of the Metropolitan line last weekend and restrictions on the Circle, and Waterloo & City lines, RMT union general secretary Mick Lynch warned that more disruption was “inevitable”.

* Tobias Ellwood, chair of the Commons defence committee, said: “The urgency of staff shortages now impacting on supermarkets and by extension national food distribution warrants a Cobra meeting today for which the deployment of the Army to assist in HGV driver shortfall should be a last resort option considered.” Mr Kwarteng told LBC Radio: “As far as I know we’re not looking at bringing in troops.”

* A number of English councils have been forced to cancel bin collections due to staff self-isolating. Richmond is delaying garden waste collections.

* Sandwich chain Pret has temporarily closed 17 shops due to staff being forced to self-isolate.

* Fuel retailer BP said it had closed several sites temporarily because of a shortage of fuel but it stressed the main reason was a lack of qualified lorry drivers.

* Mr Kwarteng said a decision on whether to end the self-isolation rules on August 16 for the double-jabbed would only be taken the week before, although, he added: “I fully expect restrictions to be lifted.”

* Food distribution company Bidfood, struggling with staff shortages, is advising workers who are “pinged” by the app to follow a testing regime and continue working if negative, in breach of the Government’s advice.

The chief executive of the British Retail Consortium warned that food retailers would be forced to close more stores because of the number of staff being told to self-isolate by the NHS app.

Speaking to BBC Breakfast, Helen Dickinson added: “There will be many smaller businesses where if they only have one or two staff and they need to self-isolate, then that’s them needing to close their doors completely.”

Ian Wright, head of the Food and Drink Federation, told the Government to “pull their fingers out,” adding: “We need to get this sorted soon, or what will happen is that people will vote with their fingers and turn off the app.” Ms Dickinson also said she was hopeful the Government might shift its position on self-isolation rules for food supply chain workers “in the coming hours”.

Mr Kwarteng said the Government was “absolutely committed to vaccine passports” for nightclubs and some other large venues, and insisted the plan could get through the Commons despite the threat of it being blocked by rebel Tory MPs, Labour and the Liberal Democrats.