Environmental groups will on Friday mount a fresh attack on the government’s rationale for supporting more coal, publishing a study that suggests no new stations will be needed to bridge the looming “energy gap”, provided the UK’s energy efficiency and renewables targets are met.

The research will intensify the pressure on Gordon Brown, prime minister, to rescind his backing for Eon’s proposed new £1.5bn ($3bn) Kingsnorth plant in Kent, either by referring it to a public inquiry and so delaying development by years or rejecting it altogether.