OTTAWA - Prime Minister Stephen Harper says the Commonwealth's original climate-change plan would have meant a doubling of greenhouse emissions over the next 50 years.

Harper told the House of Commons that is one reason why Canada blocked an agreement last weekend in Uganda, which would have seen the organization set binding targets for reductions.

It's unclear what scientific studies Harper used to make the statement, but he says it would have been irresponsible to agree to a deal that would have forced some countries, but not all, to cut emissions.

The opposition Liberals and Bloc Quebecois took turns hammering the Conservatives over the results of the Commonwealth summit, which critics have said shamed Canada on the international stage.

Liberal Leader Stephane Dion says he wonders whether Environment Minister John Baird will sabotage the coming United Nations conference on climate change the way Harper sabotaged the Commonwealth summit.