Hundreds of hotels in the UK have poor food hygiene ratings, some which need improvement urgently, but are withholding this from public view.
A total of 652 hotels - including one with five stars and two with AA Rosettes - B&Bs and guesthouses have ratings that indicate improvement is necessary.
Each of the establishments received a rating of two or below from their local authority, based on the Food Standards Agency's (FSA) 0-5 scale, according to Which? Travel.
Under current legislation, however, hotels in the UK and Scotland are not required to publicly display ratings, unlike in Wales and Northern Ireland.
Among the under-achieving hotels were London's five-star Royal Horseguards in Westminster and four-star Novotel in Birmingham.
Both received a hygiene rating of just two, with Novotel's rating being for "high-risk food... out of temperature control".
The worst ratings included four-star Copthorne Hotel in Birmingham, which scored one, where inspectors discovered raw meat stored next to sauces in a fridge as well as out-of-date seafood.
Best Western's Dean Court Hotel in York, which boasts two AA Rosettes, was also awarded a one rating for food hygiene.
Which? Travel sent undercover researchers to eight hotels in London, Birmingham and Northumberland with a food hygiene rating of between zero and two, finding that not one visibly displayed its rating at the time of the visit.
Hotels, B&Bs or guesthouses are not currently required to publicly display ratings, but Which? are calling for this to be made mandatory.
The FSA is currently contemplating such a scheme.
Which? Travel editor Rory Boland said: "Around nine in 10 of us eat at least one meal in our overnight accommodation so it's vital that hotels, B&Bs and guesthouses have high standards of food hygiene.
"We know that displaying the rating outside the premises encourages higher standards, which is why we support the FSA case for a compulsory display scheme for the whole of the UK."