Motorists may want to think carefully about which motorway service stations they use after analysis found 10 locations have food outlets failing to achieve "good" hygiene standards in their most recent tests.
Inspection reports released following Freedom of Information (FoI) requests by the Press Association revealed that problems include meatballs at a Subway not being kept warm enough and the risk of E.coli at a branch of the healthy eating chain Tossed.
Both companies said the issues raised by the inspectors in June last year have since been dealt with.
Analysis of hygiene ratings found that services in the south-east of England are three times more likely than the rest of Britain to have at least one food business failing to achieve a score of four out of five.
Five out of 23 rest stops (22%) in south-east England fell into this category following tests in the past 18 months. This is compared to five out of 69 in the rest of Britain (7%).
Two of the M25´s four services - Cobham in Surrey and South Mimms in Hertfordshire - have outlets which scored below four following last year's inspections in January and June respectively.
The Food Standards Agency (FSA) says a rating of four must be achieved for a food outlet to be classed as having "good" hygiene.
Branches of Tossed and international fast-food chain Subway at South Mimms were both warned that there is "improvement necessary" after scoring just two out of five.
Documents released by Hertsmere Borough Council following FoI requests reveal that its inspectors found Subway's meatballs were being kept four degrees below the 63C minimum temperature. They also discovered "inadequate facilities for washing food".
The inspection of Tossed found that its system for washing fruit and vegetables could not be "wholly relied on" for dealing with E.coli. It also noted that products which were "likely to support the growth of food bacteria" were being kept at an unsuitably high temperature in a display chiller.
Beaconsfield on the M40 in Buckinghamshire is the only service station found to have an outlet scoring zero, with inspectors warning its branch of The Carvery Express in January that there is "urgent improvement necessary".
El Mexicana, at the same location, was rated just one out of five in October 2015 - meaning "major improvement necessary".
Fleet on the M3 in Hampshire and Baldock on the A1(M) in Hertfordshire also host outlets which scored below four, in November 2015 and January 2016 respectively.
Outside of the South East the worst performance is at Peterborough services where an El Mexicana scored just two in September last year.
A Subway spokeswoman said the company has been assured by the manager of the South Mimms store that "action was taken to address concerns" following the inspection.
Tossed issued a statement in response to the inspection of its branch at the same services which read: "This was an isolated incident which was dealt with at the time. A request was also made to have a site revisit last June and we await a response."
A spokeswoman for El Mexicana said: "The issues raised were very specific towards particular staff actions, both of which have been addressed. We expect the urgent requested re-visit to reflect a score consistent with our normal exemplary hygiene star rating."
Andrew Long, chief executive of Extra Motorway Service Area Group, which is the landlord owner of Baldock, Beaconsfield, Cobham and Peterborough services, said the company's tenants are responsible for maintaining standards.
He told the Press Association: "If Extra becomes aware of any matter where the tenant is not operating to the required standards, then Extra takes appropriate action to ensure that the respective tenant does quickly address any shortfall in their own operating standards."
Long added that the reasons behind the "less than acceptable" ratings at its services have been addressed by the tenants.
A spokesman for Welcome Break, which owns South Mimms and Fleet services, said food hygiene is of "paramount importance" at its service stations.
He added that following the inspections at South Mimms the company "put actions and improvements in place to ensure that standards in all of our locations are at all times what our customers expect".
No-one at The Carvery Express could be contacted for a response.