The Salvation Army centre in Harrington Street put out a desperate appeal for donations after shocked staff revealed "we've hardly anything left."
The food bank, one of 10 operating in the city, hands out 800 bags of groceries and toiletries a month to people below the poverty line.
But Claire Bowerman, the charity's community centre co-ordinator, revealed the service is at crisis point and may have to ration supplies to make sure no-one misses out altogether.
"It's pretty grim here," she confessed as she surveyed the empty shelves. "Although we've got plenty of pasta and cereals, we've practically run out of everything else.
"I don't know why, but donations of food just aren't coming in like they were. It could be a result of the pandemic, or it could just be people are becoming charity weary.
"But unless we can get supplies we are facing a very difficult time, especially with the school summer holidays not far off."
Claire pledged the food bank, one of the biggest in the city, will not shut its doors, although keeping up its proud record of helping the needy is proving increasingly difficult during Covid.
"There is no suggestion we will have to close - the Salvation Army will always find a way of providing food for those in desperate situations," she said. "We always have done and we always will do.
"But we are in real need of food right now. We do get some financial donations and they are very welcome. I have just put in a £600 order for supplies today. But that will be delivered tomorrow and will all be gone by Monday.
"We would never turn people away, but we may have to cut down what we give them to make sure what little we do have goes further. That will be very sad, but there might be no other option."
Tinned and dried food - excluding pasta and cereals - are crucial if the centre is to continue meeting the needs of families and individuals referred to it for help.
Demand has increased during the Covid crisis, with an average of between 40 and 50 referrals a week almost doubling due to people finding themselves unemployed or on reduced pay due to furlough.
But public donations made directly to the centre, at churches, online, or at supermarkets in the city have been well down on usual.
"To be honest I'm not really sure why that's happening," said Claire. "Maybe many more people are struggling for money and just can't afford to give like they did.
"What is worrying is the school holidays. That is always a difficult time for us. We are always very stretched over that summer period and the way things are going right now it is going to be extremely difficult to help all those we need to help.
"The extra month of restrictions announced by the Government yesterday isn't going to help. But we will carry on regardless and hope that people see this appeal and help us out of such a critical situation."
The centre says it has had added pressure on its resources in recent months due to problems with Government payment cards for refugees and asylum-seekers.
To donate you can take foodstuffs and toiletries to the Salvation Army centre in Harrington Road (between Moor Lane and Adelphi Street) between 10am and 1pm.
Donations can also be made through online shopping and in special trolleys at both Morrisons store on the Docks or Sainsburys in Deepdale.
You can also call the charity in advance on 01772 555425 to find out what items are in particularly short supply. Or you can email them at: [email protected]