The Kathleen Wynne government has budgeted $5.5 million for advertising to tout its cuts to hydro bills, according to documents revealed on Monday.

The New Democrats obtained the documents through a freedom of information request and NDP leader Andrea Horwath says they show the government is spending taxpayer money to promote the Ontario Liberal Party.

The documents include a business case from the Ministry of Energy in March that shows $1.5 million approved for an advertising agency to produce the campaign to promote the Fair Hydro Plan, plus $4 million to buy air time.

"The number is eye-popping," Horwath said in Question Period. "This advertising campaign is expensive. It was clearly thought up to help the premier and her Liberal Party bounce back in the polls."

In addition to revealing the costs, the documents also reveal how worried the government was about the beating it was taking over hydro prices.

"Despite recent cost reduction actions the government has implemented, the overriding messaging from media has been unreasonably high costs associated with electricity," said a briefing note from the Energy Ministry dated Feb. 2. "The value of what people are getting for their money has been overshadowed."

Treasury Board president Liz Sandals defended the ads as necessary.

"People find the (hydro) bills quite confusing," Sandals told reporters at Queen's Park. "We want to make sure that people actually know what's going on."

The documents show the Liberals spent $1.16 million advertising the hydro plan by the end of March, less than a month after Wynne announced it.

Horwath accused the government of aiming to run the ads in the run-up to the provincial election, scheduled for next June 7.

However, legislation explicitly prohibits government advertising in the 60 days before the scheduled start of an election campaign.

"We will not be running fair hydro ads during that period," Sandals said in Question Period.