Facebook should "take responsibility" for people using its website to sell food from their own homes, the Food Standards Agency has said.
The watchdog is warning that sellers who have not registered with or been inspected by their local councils could be putting the public at risk.
FSA chairwoman Heather Hancock wants Facebook to bring in stricter seller checks on its Marketplace platform.
Facebook says its sellers must follow all applicable laws and regulations.
Facebook Marketplace allows users to post advertisements for free, to sell a range of goods and services.
But rules in force across the UK require people selling food from their homes on a regular basis to register with their local authority. Once registered, they may be inspected and given a food hygiene rating.
BBC News found a wide variety of food for sale by unregistered sellers on Facebook Marketplace.
This included cooked meals and baked goods - and in one case, a whole deer.
Food safety expert Tony Lewis looked at a number of the adverts.
"There is no information about what they contain, we don't have a list of ingredients," he said.
"How's it been stored, how's it been prepped, have we got a whole load of allergens in there?"
He also warns about the potential risk to health.
"Listeria is a real threat, in the worst case it could kill you."
The BBC conducted a series of test purchases across the Midlands, buying goat curry, cake, roast chicken and chocolate party cones for children from sellers advertising on Facebook Marketplace.
None of the sellers indicated they were registered, had been inspected or had a food hygiene rating.
One said they thought those regulations did not apply to people cooking in their own homes.
Another, when asked about the possible presence of allergens admitted: "I haven't actually checked."
Ms Hancock of the FSA, which is responsible for food safety in England, Wales and Northern Ireland, says Facebook has "an unavoidable moral obligation to help keep people safe".
She said "if something goes wrong with this food", the sellers would be in a "terrible mess personally, about the consequences for them and the risk that they're posing to other people".
She added: "We'd like that responsibility to extend to asking anybody who is supplying or selling food through the platform - are they registered?"
She also wants sellers to be forced to display any food hygiene rating they obtain.
Facebook said: "The safety of our community is our foremost priority and if we determine that a listing violates any of our community standards or commerce policies we will immediately remove the listing."
It added: "We're in contact with the FSA to discuss the concerns raised and what we can do together on this issue."
'Can be done safely'
Tanya Ednan-Laperouse, whose daughter Natasha died in 2016 from a severe allergic reaction after eating a sandwich from High Street chain Pret a Manger, says Facebook must do more, especially when it comes to allergens.
Natasha did not know her sandwich contained sesame seeds and after she died her parents successfully campaigned for changes in the law. Food businesses will have to include full ingredients labelling on pre-packaged products by summer 2021.
Mrs Ednan-Laperouse says she does not want to stop people selling homemade food, but is demanding they label ingredients clearly.
Informing buyers on the doorstep is not enough, she said, adding: "People can get confused, they might forget... Someone might misunderstand what they're saying."
Paula Wilkinson runs a business called Mums Bake Cakes, which connects home bakers to customers via a dedicated website.
She makes sure all her sellers are registered and insured.
There is "absolutely" no reason why properly-registered people should not sell food they have prepared at home, she says.
"It can be done safely," Ms Wilkinson added.