The coolant, which is already in use in over 2 million cars, has caused controversy already between carmakers and the EU. R1234yf is currently the only commercially available refrigerant with a sufficiently low global warming potential (GWP) to comply with the requirements of new standards introduced by the EU in 2006 to help reduce harmful emissions and combat global warming.

Yet carmaker Daimler has refused to use the new refrigerant, claiming it is too flammable, which briefly led to France banning some Mercedes cars that used the substance. Last month saw Germany ordered by the European Commission to force the carmaker to stop using older, more polluting coolants.

Now the EU has said that the deal between Honeywell and DuPont on developing the new refrigerant ‘may have limited its availability and technical development, in breach of EU antitrust rules’.

It added that Honeywell and DuPont are the only two suppliers of R1234yf to carmakers and its provisional finding is that the cooperation between Honeywell and DuPont on production of R1234yf has reduced their decision-making independence and resulted in restrictive effects on competition.

In response, Honeywell said that the allegations outlined in the Statement of Objections are ‘baseless and conflict with the EU's own laws that encourage collaboration on development’.

It added that: ‘Honeywell is confident that our practices are consistent with the law and that the Commission will conclude that we acted in full compliance with European Union competition rules.

‘By collaborating on expensive and risky development, Honeywell and DuPont were able to develop HFO-1234yf in time to meet the MAC Directive's 2017 deadline.

‘Honeywell's and DuPont's work also ensured a competitive market for HFO-1234yf. Honeywell and DuPont are marketing HFO-1234yf independently and in direct competition with one another.’