The Pembina Institute is defending its consulting contracts with the City of Calgary after criticism from the Canadian Taxpayers Federation.

The federation said on Thursday that it was in appropriate for the city to hire the environmental think tank and advocacy group to prepare reports.

Ed Whittingham, the executive director of the Pembina Institute, said on Friday his organization's advocacy work is separate from its consultancy work.

Whittingham said the institute was hired because of its technical expertise to help the city with its strategy on greenhouse gas emissions.

"When we're hired by, whether it's an energy company or a government, a federal or provincial government or a municipality, it's because we've got the expertise to produce deliverables for our clients and that's what we focus on."

The plan put together by Pembina for the city was debated publicly, added Whittingham.

Mayor Naheed Nenshi is defending the use of the Pembina Institute, saying contracting out such work to experts saves money for taxpayers because it saves the city form hiring more workers.