Blood on the mayonnaise, mouldy meat, toxic potatoes and a dead rat in the kitchen are just some of the reasons why some of the borough’s businesses were given the lowest possible rating for food hygiene over the past year, the Gazette can reveal.

The reports, released under a freedom of information (FOI) request, show that no fewer than 20 restaurants, cafés and supermarkets across Islington failed to meet basic food safety requirements in 2013 and were awarded zero out of five for hygiene.

Some venues were so filthy that inspectors had no choice but to order them to cease trading immediately, and four are facing prosecution after failing multiple tests – most were forced to make “major improvements” or face legal action.

The sobering reports, which run to nearly 100 pages, expose a series of grisly findings, including evidence of mice and rat droppings, cockroaches, pests, grime on the walls and poor staff hygiene.

In one incident, Chicks on Fire, on Hercules Street, Holloway, voluntarily closed for a complete clean-up after a dead rat was found in the kitchen.

Hassan Hasan, chef at the restaurant, said: “We were horrified when they found it. We know there is a big problem with rodents in the area but we had no signs of droppings or anything like that.

“We have no problems with cleanliness or hygiene – as soon as we found out we voluntarily shut for three days and disinfected the entire place.”

Salim’s Hotspot in Holloway Road, Holloway, was slammed in May 2013 after an inspector found evidence of blood on the lid of a bottle of mayonnaise.

Meanwhile an inspection of the North London Wine Cellar, in Newington Green Road, Newington Green, found evidence of mice infestation.

The shop was condemned after environmental health officers discovered that food was being stored outside – including a suggestion that vegetables had been gnawed by rodents overnight.

The store was also found selling a packet of mouldy chorizo.

At Eren Local Mini Market in Highbury New Park Road, an examination of the premises found green potatoes – which can be toxic – and unlabelled bread for sale.

Staff were also criticised for placing rodent poison next to an area where food was kept.

Councillor Rakhia Ismail, Islington Council’s executive member for sustainability, said: “Premises which fail these inspections are subject to enforcement action and any that pose a serious risk to public health are closed immediately.

“The latest food hygiene ratings for food businesses can be found on the Food Standard Agency website.”