Nearly a third of all business inspected in Merton over a 12 month period were given written warning for food hygiene issues.

More than 400 warnings were handed out due to problems such as cleanliness and separation of foods.

Data from the Food Standards Agency shows the results of food hygiene intervention inspections in the local authority, over the 12 months to April.

The businesses inspected are mostly restaurants, but include any establishment which handles unpacked food including farms, manufacturers and catering companies.

Inspectors assessed 1,361 businesses and handed out 421 written warnings in Merton.

Councillor Nick Draper, cabinet member for community and culture said: “We take seriously our responsibility to ensure all food premises in Merton, are clean and adhere to food safety standards.

"We are committed to cracking down on establishments that fail to comply with our requirements.

"Last year we carried out 949 visits to food premises across the borough and 421 warning letters were sent to businesses where our inspectors raised concerns."

Any breach of food hygiene regulations can lead to a written warning. Breaches include problems with cleanliness, training of staff, record keeping, washing facilities and separation of cooked and raw foods.

Officials consider the seriousness of the case, as well as the co-operation of the business, before deciding on what action to take.

As well as the written warnings, in Merton there were five voluntary closures, four hygiene prohibition notices, two hygiene improvement notices, one food seizure and one caution. Inspectors carried out one successful prosecution in court, for food hygiene breaches.

High risk scores were given to seven businesses. This means they need to be inspected again within six months.

Mr Draper added: "A warning letter may be a detailed report for a poor premises to perhaps something shorter pointing out a few minor compliance issues to a well-run establishment.

"We are planning to introduce an easier and more transparent method of recording warnings when Wandsworth fully joins the Regulatory Service Partnership in November.

"Across Merton, there has been a gradual, year on year increase in food premises obtaining a Food Hygiene Rating of three and above, from 92% in 2017 to 93% in 2018.

"This is a fantastic achievement for Merton and a great reflection of the hard work put in by our small food safety team who work closely with business owners to improve standards and protect the health of our residents.”

This rating is different from the 0 to 5 score that restaurants and takeaways display in their windows, as it is an indicator of when officials need to assess the business again.

A business which gets a high risk rating is "highly likely" to have breached food hygiene regulations, according to the FSA.

However it could also be because of its trade, such as large scale manufacturers with lots of customers or businesses that carry out specialist procedures.

Nina Purcell, director of Regulatory Delivery at the FSA, said: "It’s encouraging that local authorities have made improvements in the percentage of interventions achieved and are continuing to target their activities at food businesses where food safety risks are the highest or where food fraud is more likely."