The government is scaling back plans to fight greenhouse gas emissions, cutting funding for programs to buy electric vehicles and develop charging stations, and delaying construction of 31 kilometres of HOV lanes because of shrinking revenues.
The need to cut spending to help eliminate a $14.4 billion deficit is no reason to cut good programs that help reduce the impact of climate change, said Miller.
"The amounts of money we're talking are small relative to the fiscal challenges of the government. I don't think you can explain it by that," said Miller.
"That's more of an excuse than the cause."
Environment Minister Jim Bradley said the government cut $101 million from the $164 million promised for electric vehicles and charging stations because so few people took advantage of the program.
"This is unfortunate, but the demand was not as great, I think in all jurisdictions, for those electric vehicles as we had hoped," Bradley said in an interview.
"There was a lot of anticipation that people would be moving forward in the purchases, but despite the rebates and incentives, it has not moved as quickly as possible."
Ontario offers rebates of up to $8,500 for the purchase of an electric vehicle, but there was little public knowledge of the other programs that had their funding cut, said Miller.
"Certainly it's not been aggressively promoted," he said.
Miller gave the government high marks for phasing out coal-fired electricity generation, but said that has meant natural gas has surpassed coal as the largest source of greenhouse gas emissions in the energy sector.
"While the coal phase-out is a worthy accomplishment, it is now past performance and no new initiatives to garner such measurable benefits or reductions are being advanced," he said.
"Clearly the Ontario government's commitment to responding to GHG emissions and climate change has become questionable."
Miller also singled out the transportation sector as a special concern, saying it is now the single largest source of the unwanted emissions.
"If we can shift some of our transportation to electricity drive, which means heavy rail, certainly light rail to move people, and plug-in electric vehicles, then we'll save large amounts of greenhouse gas emissions," he said.
The government is planning to use diesel locomotives on its new rail link from Toronto's Union Station to Pearson International Airport and later switch to more environmentally-friendly electric trains.
Bradley said it cost more to use electric trains than diesel, but he agreed it's the way to go in the future.
"When you start to electrify what happens is you're able to do fewer projects, but nevertheless we are moving in that direction," he said.
Miller's annual report on climate change also takes the Liberals to task for "a complete lack of engagement around the question of carbon pricing," and urges action.
"Other jurisdictions are demonstrating that carbon pricing can be adopted without hurting economic growth, while delivering the benefit of lowered GHG emissions," he said.
"B.C. did it and survived at least one election, Quebec has a price on carbon, Alberta has a price on carbon _ that would be all the other major provinces."