Pret said the patron died after eating a “super-veg rainbow flatbread” containing a yoghurt that was supposed to be dairy-free, but was found to be contaminated with dairy.
The Food Standards Agency (FSA) said it investigated supplier CoYo, which then issued an allergy alert and recalled its coconut yoghurts.
But CoYo has denied the recall was linked to the woman’s death and accused Pret of hampering its own inquiry by failing to provide vital information.
“The claims made by Pret are unfounded,” a spokeswoman for CoYo said yesterday.
The latest death emerged as Pret was facing scrutiny over 15-year-old Natasha Ednan-Laperouse, who was allergic to sesame and died after eating one of its baguettes.
The second customer collapsed and died on 27 December last year after buying the sandwich in a store in Stall Street, Bath.
Pret said it had been “mis-sold” a guaranteed dairy-free yoghurt by CoYo that was discovered to contain dairy protein.
Vegan brand CoYo, a coconut milk brand that has been endorsed by TV cook Nigella Lawson, recalled the yoghurts in February. But yesterday, CoYo denied this was related, saying that product was supplied to it in January – after the woman’s death.
“The dairy-free product we provided to Pret in December 2017, at the time of this tragedy, is not linked to the product we recalled in February 2018,” a spokeswoman said.
“Pret’s inability to provide us with a batch code, despite several requests, has severely limited our ability to investigate this further.”
Bath’s council alerted Pret to the incident and the chain said it then withdrew all affected products, ended its CoYo contract and launched legal action.
“Subsequent testing by Pret and two independent authorities found that the CoYo dairy-free yoghurt contained traces of dairy protein,” a Pret spokesman added.
The Food Standards Agency investigated along with Bexley council in London, where CoYo is based, before it issued an allergy alert.
Pret announced on Wednesday it will include full ingredient labelling on all of its products and the Government is considering a law change after the death of Natasha, from Fulham, south-west London.
She collapsed on board a flight in July 2016 after eating an artichoke, olive and tapenade baguette she had bought in Heathrow Airport.
Natasha’s parents, Nadim and Tanya Ednan-Laperouse, said in a statement through lawyers Leigh Day: “We were incredibly saddened to learn of someone else losing their life from allergens in their food.
“Our hearts go out to the bereaved family.”