NHS staff are being targeted by muggers trying to steal their identity badges so they can use them to obtain the free food and drinks being offered to doctors and nurses tackling coronavirus.

Health service bosses are so concerned by a spate of incidents that they are preparing to warn all hospital staff to hide their NHS lanyards when they are arriving at or leaving work.

NHS England condemned attempts to rob staff as “the actions of an idiotic few”.

Last week robbers tried to grab badges belonging to two personnel at Lewisham hospital in south London but did not succeed. The muggers approached the two staff – thought to be doctors – as they were walking through a park just outside a rear entrance to the hospital.

One of the doctors’ colleagues said: “Something like this is appalling. It’s beyond the pale and so shocking. Someone tried to grab my colleagues’ ID badges as they were leaving but didn’t get them.”

All staff at the Lewisham and Greenwich NHS trust’s two acute hospitals have now been told to keep their lanyards concealed when they are entering or leaving the premises. The trust’s all-staff briefing issued on Monday said: “Following reports of an attempt to take the ID badges of two members of staff as they were leaving work, please make sure your ID badge is out of sight.”

Those trying to steal ID badges are thought to want them to obtain the free coffee, pizza and other products that high street chains such as Leon, Domino’s, Costa Coffee, Pret a Manger, Burger King, Pizza Hut and Greggs have begun offering NHS staff to thank them for their efforts in dealing with the coronavirus epidemic.

An NHS official said: “This is absolutely grim. ID badges are being stolen in a few places as staff come out of their trust. As soon as staff are coming off-site they are waiting for them and stealing them, to get the free food and also so they can go shopping during the protected early morning shopping hour that some supermarkets have put in place for NHS staff.

“It’s mainly nurses who have been targeted. They’re the ones who often walk out of the main entrance of a hospital with their lanyards on.”

A Metropolitan Police spokesperson said: “We are aware of these messages which were shared in good faith but have been unable to identify any reported crimes that correspond to the concerns. Where other crimes have taken place we can find no evidence to suggest that those involved were deliberately targeted because of their role in the health service. If any member of NHS staff has been the victim of any crime in these circumstances they should contact the Metropolitan Police as a matter of urgency.”

NHS England is finalising new advice that it will send to all 240 trusts in England, asking them to tell staff to be vigilant and to keep their ID badge hidden.

Ruth May, its chief nursing officer, said: “Our NHS staff are pulling out all the stops in the face of an unprecedented global health threat, so these reports are really concerning. We have seen some extraordinary acts of generosity from businesses and the public and this will not be overshadowed by the actions of an idiotic few, but I would urge everyone to show NHS staff the gratitude they deserve and help them to do what they do best.”

Several departments at University College Hospital London, a major acute trust in the centre of the capital, have recently advised their own staff to beware after several incidents. Trust bosses then issued a briefing to all personnel on Monday repeating the need to be careful.

It said: “We are doing what we can to keep you safe. Please raise your vigilance and do not have your mobile phone or NHS lanyards/ID visible outside our hospitals. Please remember to report any incidents to security at UCLH too.”

• This article was amended on 6 April 2020 to include a response from the Metropolitan police.