The Greens' sole Assembly member told the Belfast agm he would continue to oppose the executive, but would also "pledge to work to provide a stable administration".
Brian Wilson, the North Down Assembly member, criticised the Executive for "making Green claims but failing to live up to them".
In particular he referred to what he called "a betrayal of sustainable energy installers by the ending of 'Reconnect' grants" - a programme of capital grants for homeowners to install renewable energy systems such as solar water heating and heat pumps.
He also criticised the "delay in setting up an independent environmental protection agency" for Northern Ireland and what he called "inadequate funding for expansion of public transport".
Mr Wilson also referred to proposals to rely more on nuclear power.
The special conference announced a "Green Wash" award - for an individual or company who has damaged, or threatens to damage, the environment.
The winner of the mock "award" was the DUP's Sammy Wilson, East Antrim MP and Assembly member, in recognition of his support for nuclear power in Northern Ireland and his public questioning in the Assembly of the fact of climate change and global warming.
Criticism of the Stormont executive also came from the Greens' co-chair in Northern Ireland, Dr John Barry.
He cited the "the short-sighted decision by Minister [ Nigel] Dodds to end the Reconnect grants, which have been a central part in building up the micro-renewable industry".
He also condemned what he called finance minister Peter Robinson's "refusal to ensure building regulations which would . . . improve the energy efficiency of housing, thus saving money for homeowners as well as saving the environment".
Environment minister Arlene Forster was also criticised for her "refusal to fast-track the establishing an independent environmental protection agency", making Northern Ireland the only part of these islands not to have such an agency.
Referring to the Rev Ian Paisley and Martin McGuinness he added: "Instead of pushing for the greening of the Northern Ireland economy, what we have is the rather pathetic spectacle of the First and Deputy First Minister pushing for Donal Trump's golf green to be located in Northern Ireland."