OTTAWA — A former top aide to Prime Minister Stephen Harper has formally pleaded not guilty to an influence peddling charge as his trial begins.

Bruce Carson is charged in connection with the proposed sale of water purification systems to First Nations communities.

The trial is another legal distraction for the Harper government as it campaigns for re-election.

As the trial started, Harper’s opponents were already attempting to link him to the case.

Liberal Leader Justin Trudeau refers to Carson as just one in a long list of dubious Harper appointments.

The court has been told Carson testified in preliminary evidence he was merely trying to help when he offered to assist an Ottawa-based company, H2O Water Professionals, in getting meetings in 2010 and 2011 with government officials.

But Crown Attorney Jason Nicol told the Ontario Superior Court of Justice that Carson wasn’t just some altruistic figure trying to help H2O Pros clinch a deal to sell water purification equipment.

The Carson case follows on the heels of the trial of Sen. Mike Duffy, which forced the Conservatives off of their campaign message over a two-week period in August.

The Canadian Press