The father of a teenager with multiple food allergies who collapsed on a British Airways flight has described the inquest into her death as a “watershed moment” that should prompt a change in the law and save the lives of others.

Natasha Ednan-Laperouse, 15, from Fulham, south-west London, collapsed on a flight from London to Nice on 17 July 2016 after eating an artichoke, olive and tapenade baguette she had bought from a branch of Pret a Manger at Heathrow airport’s Terminal 5.

The baguette did not have any allergen advice on its wrapper. Reduced labelling requirements for food produced on site meant it was sufficient for general allergen warnings to be posted around the shop, instructing customers to consult staff for advice. The inquest heard that such regulations were designed to benefit small sandwich shops that make food in front of the customer.

On Friday, Dr Séan Cummings, the acting senior coroner for west London, recorded that Natasha died as a result of a “catastrophic anaphylactic reaction from which she could not be saved”, and said he would be writing to the environment secretary, Michael Gove, urging him to review the regulation in question and specifically “whether large food business operators should benefit”.

Speaking outside the court afterwards, Natasha’s father, Nadim Ednan-Laperouse, who was with her on the flight, said the inquest had shown the law was not fit for purpose.

Standing alongside Natasha’s mother, Tanya, and 15-year-old brother, Alex, as the family held a framed photograph of Natasha, he said: “It feels to us that if Pret a Manger were following the law then the law was playing Russian roulette with our daughter’s life. It’s clear that the food labelling laws as they stand today are not fit for purpose and it is now time to change the law. Natasha’s inquest should serve as a watershed moment to make meaningful change and to save lives.”

The coroner had strong words for Pret, criticising its labelling of products and monitoring of instances of customers suffering allergic reactions.

Natasha’s father told the inquest that no stickers warning about allergens were visible in the store, and Cummings said signs displayed on langars (refrigerated display cabinets) were “difficult to see … I am of the view that they were inadequate in terms of visibility”.

The inquest, which lasted four days, heard Pret a Manger had nine cases of similar allergic reactions in the year before Natasha died. Cummings said the chain’s system for monitoring such incidents was “inconsistent and incoherent”.

He said: “Overall I was left with the impression that Pret had not addressed the fact that monitoring food allergy in a business selling more than 200m items a year was something to be taken very seriously indeed.”

Along with the report to Gove, Cummings said he would write to Pret “in relation to collecting information on allergic reactions and responding to serious concerns”. He said that although he had heard evidence that the chain had made some changes, he considered them insufficient.

Clive Schlee, the chief executive of Pret a Manger, said the company was deeply sorry for Natasha’s death and vowed to learn from the inquest. “All of us at Pret want to see meaningful change come from this tragedy,” he said. “We will make sure that it does.”

A third report to prevent future deaths will be sent to the Medicines and Healthcare Products Regulatory Agency, and the manufacturer of EpiPens, amid concerns they may be too short to penetrate the muscle and contain an inadequate dose of adrenaline to ensure they are effective for everyone.

Cummings said a failure by BA staff to tell a passenger, Dr Thomas Pearson-Jones, who attended to Natasha on the plane, that there was a defibrillator onboard was an “omission” but did not make a material difference to the outcome, and he praised the newly qualified doctor and the cabin crew manager, Mario Ballestri, for their response to the emergency.

The coroner said Natasha had a number of trips planned for the summer and was “excited at what she was hoping to be her best summer ever”.

During the inquest, Natasha’s father described how she implored him, “Daddy, help me, I can’t breathe,” before collapsing during the flight. Later, he said, as she lay in hospital in Nice and he was told she would not survive, he had raised the phone to her ear so her mother and brother could say goodbye, and he cut off a lock of her hair to keep.

Addressing the father at the end of the inquest, Cummings offered his condolences and said: “I can’t imagine what it was like for you on that plane.” Ednan-Laperouse, weeping, replied: “Terrible.”

Political support for a change in food regulations has come the family’s MP, Andy Slaughter, Jon Cruddas, the chairman of the all-party parliamentary group for allergy, and the deputy Labour leader, Tom Watson. Watson said the words of Natasha’s family “serve as a terrible indictment of our food safety laws and of the approach of large food conglomerates like Pret a Manger, who have demonstrably failed to show responsibility for the welfare of their customers”.

He said food producers and retailers should offer full disclosure on 14 allergens. While he expressed hope they would do this voluntarily, he said reality suggested a change of law would be necessary.