Guests are ten times more likely to award it a poor rating for cleanliness than any other hotel, while it achieved a one-star rating in nearly all categories – including bathrooms, bed comfort, facilities and value for money – and an overall score of 39%.
The group’s solitary two-star achievement was in the customer service category.
EasyHotel (58%) and Ibis Budget (60%) were the next poorest performers, but scored significantly better than Britannia.
Meanwhile, Premier Inn retained its place at the top of the rankings but had to share the crown with Wetherspoon Hotels, with both groups scoring 79%.
They were closely followed by Hilton Garden Inn (78%) and Radisson Blu Edwardian (77%), while Hilton Hampton (74%) was fifth.
Premier Inn scored five stars in the bedrooms category but only three stars for facilities and food and drink.
Wetherspoons Hotels notched five stars for value for money and bedrooms but only three for cleanliness and facilities.
The survey sought the opinions of more than 8,000 hotel guests and included more than 40 well-known hotel groups.
“There really is no excuse for the grubby bathtubs and filthy rooms that we have seen year after year with Britannia so it is best to avoid them completely and go almost anywhere else,” says Rory Boland, Which? Travel Editor.
“If you are looking for a cheap and cheerful stay in the centre of town you would be better off choosing the ever-reliable Premier Inn or a Wetherspoon Hotel, where even with paying extra for breakfast you can expect extraordinarily good value for money.”