The vast majority of Subway stores in Waltham Forest operate under a halal-only policy, it has emerged.
Seven out of eight stores across the borough substitute pork products, such as bacon and ham, with turkey-based ham and rashers, and its salami and pepperoni is beef-based.
Consuming pig-based products is forbidden under Islamic law and the halal-process sees animlas slaughtered by cutting the jugular vein, carotid artery and windpipe, with the carcass completely drained of blood.
Critics say it causes unnecessary suffering to the animals and the revelation that not all halal meat is not labelled in shops, takeways and supermarkets has prompted a national debate on the issue.
The Subway outlets offering a Halal only menu in the borough are Hall Lane in Chingford, Lea Bridge Road and Leyton Mills retail park in Leyton, Church Lane in Leytonstone, Hoe Street, Selbourne Walk and St James Street in Walthamstow.
Subway in Larkshall Road, Highams Park, is the only store to serve the traditional Subway menu containing bacon, ham, salami and pepperoni.
The 'Eat Fresh' franchise has confirmed all of its suppliers "comply with the EU animal welfare legislation as a minimum and we require suppliers of Halal products to adopt the stunning of animals prior to slaughter".
A Subway spokeswoman said: "Customers have many choices as to which store they want to visit since there are over 1,700 Subways stores across the UK and Ireland.
"All Halal meats are certified by the appropriate Halal authorities and all Halal stores have numerous signs stating that they serve Halal food.
"These are situated on the menu panels, nutritional information and in the front window of the store."
Joseph Wright, 19, of Chivers Road in Chingford is a regular customer at the Hall Lane store.
He said: "It all tastes the same; it doesn't matter too much where you eat. I understand if people do not know its pork then, yeah it can become an issue.
"Also, I do think the method of killing is a bit inhumane."
A Waltham Forest resident, who wished to remain anonymous, compared the mass selling of Halal meat as comparable to the horsemeat scandal.
She added: "There is a bit of confusion going on as people want to be made aware of what they're eating and the animal welfare side of it bother me."
Muslim Tharik Hussain, 35, of Oak Hill in Woodford Green, blamed the UK media for "scaremongering" over the isuue.
He said: "The meat doesn't have to be Halal but if it is, is shouldn't be a big issue. For Muslims it's definitely something they want to have as vegetarian options are not appealing.
"I do think the majority of Halal meat is ethically killed and stunning of animals is not more humane than slaughtering, although I do accept that not all meat labelled as Halal is ethical.
"Although transparency is essential and everybody has a right to know what meat they're consuming, but the harsh reality is, demand has gone through the roof, Halal is a cheaper option and we live in a capitalist society."
All of the major supermarkets chains in the UK sell some halal chicken, lamb and beef without labelling the products as such..