A government contract issued in the wake of the Grenfell Tower fire to investigate the toxicity of burning building materials has been awarded to a research group with links to the plastic foam insulation industry.

The Ministry of Housing, Communities and Local Government (MHCLG) has awarded the £600,000 research grant to a consortium whose members include a fire testing specialist whose research has been funded by Kingspan, the company that made some of the combustible foam used in Grenfell, and a fire engineer who has publicly opposed outright bans on combustible materials.

Two members of the winning bid team also attended a conference on using plastics in facades in Brussels last year, hosted by a plastics industry body.

A rival bid from another team was rejected by the housing ministry despite being considered stronger in terms of understanding evidence about smoke and toxicity in buildings, the Guardian understands.

The contract award comes amid rising concern over building safety with tens of thousands of homes wrapped in combustible cladding, including plastic insulation foams that release toxic gases including carbon monoxide and hydrogen cyanide when they burn.

Fiona Wilcox, a senior coroner investigating the 72 deaths caused by the Grenfell fire in June 2017, concluded that the tower was filled with smoke containing “multiple toxic substances” and that “almost all of those who died in the fire, died as a result of smoke inhalation”.

The government wants the winning team to review laws concerning how toxic fires in England are allowed to be, as well as current methods of testing materials’ toxicity. It is seeking guidance on the best approach for writing limits on toxicity into building regulation guidance.

The request for bids stated: “All smoke is toxic but there remains a question as to whether certain products produce especially toxic fire effluent that may unduly impair evacuation.”

The contract was not put out to open tender but was let through the Crown Commercial Service system, which means only pre-qualified bidders could compete.

MHCLG has not announced the winning group, saying it will do so within 90 days of the contract award. However, Prof José Torero revealed the winning team in a public declaration of interest to the Grenfell Tower public inquiry.

MHCLG did, however, confirm the winning consortium was headed by OFR, a fire consultancy. It denied any conflicts of interest and stressed that because smoke toxicity was a highly specialised field there were relatively few businesses involved in such work. It said it expected industry experts to attend conferences and seminars and that this did not prohibit them from being independent.

“Our priority is that buildings are safe for residents – that’s why we’re ensuring leading experts are involved in this important research study into the impact of smoke and toxicity on buildings,” a spokesperson said. “The procurement process was robust and in line with all standard procedures.”

Torero, a fire engineer based at University College London and an expert adviser to the Grenfell Tower inquiry, is a key figure in the winning consortium.

He has argued against banning combustible materials, telling the Scottish parliament last November: “It is not such a simple problem that we can say: ‘Ban all combustible materials,’ because the implications are extraordinary … To prevent all sorts of fires, I would like to see no combustible materials in any buildings, but we all recognise that that is unrealistic.”

He also told the chairman of the Grenfell Tower inquiry, Sir Martin Moore-Bick, who was considering recommending fire safety changes, that it was “imperative, at this stage, to recommend great caution to any changes on building design practices and approved documents [which guide the application of building regulations] until the relevant issues are better understood”.

Last November Torero attended a Brussels symposium on using plastics in facades hosted by the Modern Building Alliance, which describes itself as an alliance of “trade associations and companies that represent the plastics industry in the construction sector at the European level”. Members include Kingspan and the plastics companies Dow and BASF.

Eric Guillaume, the general manager of Efectis, a laboratory company in the winning team, last month published a study of the fire spread at Grenfell that used a mathematical model to claim that the flames would have travelled across the site faster with non-combustible mineral wool insulation than with polyisocyanurate (PIR) insulation foam. It was funded by Kingspan, which makes PIR foams for wall and roof systems.

When asked if his positions on combustible materials or attendance at the symposium presented a conflict of interest, Torero replied: “Unfortunately I cannot comment on any of the matters addressed.”

When the Guardian asked Simon Lay, the director of OFR, about possible conflicts of interest arising from Guillaume’s Kingspan-funded research on fire spread at Grenfell, Torero’s argument against banning combustible materials and his own attendance at the plastics conference in Brussels, he said: “We can’t comment on these research projects.”

Efectis UK and Ireland said it was a subcontractor on the research project and “we are not allowed to talk about it”.