Environmentalists have criticised Forth Energy's plans to build a new biomass plant and flue accessories in Leith, Scotland.
Members of Friends of the Earth Scotland have claimed that the company's proposals contain misleading figures and could have a detrimental effect on American forests.
Forth Energy and Friends of the Earth Scotland have both written to each other in order to contest their respective claims, with the environmentalists now claiming that Forth Energy's green credentials should be questioned.
Stan Blackley, chief executive of the organisation, said: "These expert American groups have hammered another nail into the coffin that is Forth Energy's greenwash claims.
"The plans would place a huge demand on already stretched American forests and be an incredibly inefficient means of producing energy."
Mr Blackley is hoping that the energy minister Fergus Ewing will see the "overwhelming evidence" opposing Forth Energy and consequently reject the firm's plans.