Pressure is mounting on the publisher of the Economist over its commercial ties with the world’s three biggest tobacco companies, after numerous senior NHS and international health experts pulled out of two more Economist Impact health conferences after the Guardian’s investigation into its links with big tobacco.

Last week, the Guardian revealed that Economist Impact, a division of the Economist Group that ran 136 events in its latest financial year, had been forced to cancel a high-profile world cancer conference in Brussels at the last minute after a backlash from speakers and those due to attend.

The investigation found that Economist Impact has deep ties with Philip Morris International (PMI), Japan Tobacco International (JTI) and British American Tobacco (BAT).

Now the future of two conferences due to take place in London also hang in the balance. Future of Health Europe was due to have more than 100 speakers and more than 550 people attending, while the AI in Health summit had about 60 speakers and more than 300 attending.

Seventeen leading UK health executives were due to speak at the two conferences. They included the chief scientific officer for England, the chief medical officer of the Scottish government, and NHS England’s national clinical director for infection management and antimicrobial resistance, as well as senior executives at a number of NHS trusts, the UK Health Security Agency (UKHSA) and the National Institute for Health and Care Excellence (Nice).

But more than a dozen prominent health experts have so far pulled out of the conference this week after the Guardian’s revelations, including Sue Hill, the chief scientific officer for England, and Matt Inada-Kim, NHS England’s national clinical director for infection management and antimicrobial resistance, as well as speakers representing Nice, the UKHSA, the Greater Manchester Integrated Care Board, Imperial Healthcare Partners, and Guy’s & St Thomas’ NHS foundation trust.

Prof Sir Michael Marmot, director of the Institute of Health Equity at University College London and a global authority on health inequalities, said: “I was not aware Economist Impact were supported by big tobacco companies when I accepted the invitation to speak at this event. Now I am aware, I will no longer be appearing at the conference. I have never and would never work with the tobacco industry, and I am disappointed these details were not disclosed in advance.

“As my Marmot Review for Industry showed, I think it is vital that business plays a role in promoting health equity. However, this kind of sponsorship is unhelpful and gives mixed messages.”

Dr Raghib Ali, the chief executive of Our Future Health, said: “I had no idea that the Economist Impact programme was linked in any way with the tobacco industry when I originally agreed to speak at their event. I have now withdrawn from the event. As a doctor who has worked for many years in A&E departments, I have seen the devastating impact that tobacco has on people’s health and the burden it imposes on our NHS.”

International health experts have also withdrawn from the conference. A spokesperson for the Organisation for Economic Co-operation and Development (OECD) confirmed that Francesca Colombo, the head of its health division, was no longer speaking and that the OECD would “no longer be represented at the Future of Health Europe event”.

Andrea Feigl, the chief executive of the US-based Health Finance Institute, which aims to improve access and financing for healthcare, has also withdrawn.

Cary Adams, the chief executive of the Union for International Cancer Control, said: “Promoting knowledge about health while maintaining ties with the tobacco industry creates a true conflict of interest far beyond cancer. As a membership organisation we have informed our community of the links we have discovered, and it is clear from the response that others share our view.”

The three tobacco companies, which own some of the world’s most popular cigarette brands including Marlboro, Benson & Hedges, Dunhill and Pall Mall, have multimillion-dollar contracts with Economist Impact, extending to editorial coverage, which commonly has a pro-tobacco angle, and event sponsorship.

One online piece sympathetically positions PMI as akin to a car manufacturer moving from polluting combustion engines to cleaner alternatives for consumers. Another piece, by JTI, argues that governments should stop increasing taxes on cigarettes to keep them affordable and increase excise duties to help “limit budget deficits”.

And BAT is a top-level platinum sponsor of Economist Impact’s Sustainability Week conference in London next March.

A spokesperson for the Economist Group said: “We are in active dialogue with our health partners to determine how we can continue to convene events that have proven to be valuable to the world’s leading health organisations and experts.

“At Economist Impact, our work with sponsors is governed by guidelines that safeguard our events’ independence, quality and integrity. We accept sponsorship from companies provided the work will be undertaken independent of their influence. We have a longstanding policy that we do not accept sponsorship from tobacco companies for Economist Impact’s healthcare-related work or events, including the Future of Health and the AI Health summit.”