The man who helped David Cameron to burnish his green credentials by fitting solar panels to the roof of the PM's home accused him yesterday of "lying" over his commitment to the environment.  Brian Evans, who installed the system at the Camerons' London home in 2006, criticised the PM for "destroying" the solar electricity industry by slashing state subsidies for feed-in tariffs by more than half.  Mr Evans, who runs his own solar panel installation business, said he was being forced to lay off his only two employees because the Government was cutting funding for homes that generate solar electricity.  Mr Cameron paid about ?4,000 to have three solar panels fitted to the roof of his house in North Kensington in 2006 - at a time when the Tory leader was laying claim to the environmental agenda.  But the Prime Minister now stands accused of selling out the green movement by authorising a drastic cut in the rate of feed-in tariffs for householders with solar panels. The new rate - 21p per kilowatt hour, cut from 43p per kwh - is being introduced next month, to the anger of environmental campaigners and businesses.  Last week The Independent on Sunday revealed how Mr Cameron was facing a widespread revolt over solar electricity, with a letter signed by 55 business groups and individuals condemning the move.  Mr Evans, 47, told The IoS that Mr Cameron's decision to install the solar panels - alongside a solar thermal system and a wind turbine - now appeared to be "tokenistic". He said: "Installing the three systems meant he could lay claim to his green credentials. It enabled him to say he had renewable energy on his property. It is the case that Cameron wanted his green credentials to be visible to the world. But I don't think he has any green credentials. I think he has yellow credentials - making decisions from a cowardly position. He and others in government got into government through lies. Even though they weren't lies at the time, they became lies because they don't have the strength to stic