The renewable energy industry and Queensland Labor have called for an investigation into allegations that state-owned firm Energex manipulated data in order to push up power prices.

Cally Wilson, a former treasury analyst at Energex, told the Courier Mail that staff were asked to manipulate data in order to artificially boost revenue.

Energex is reportedly suffering a shortfall in anticipated revenue, with falling demand, partially driven by the strong take-up of solar in Queensland, a key factor. The Australian Energy Regulator sets a cap on what the energy company is allowed to recover from households.

Wilson said that she was asked to look for a debt interest rate that would make it appear that Energex’s costs were greater than they actually were.

It is unclear whether this was included in a report sent to the energy regulator as part of its deliberations on the power price caps, which are set every five years. Queensland’s household electricity bills have risen sharply over the past two years.

Energex has denied Wilson’s allegations, claiming that while she was asked to find the top interest rate in the world market, others were asked to work out the lowest rate. However, an internal company review has been launched.

Annastacia Palaszczuk, the Queensland opposition leader, said there needs to be an investigation to see whether Energex deliberately attempted to drive up prices.

“These are serious allegations that need a thorough investigation by not only the regulator, but I also believe that there should be a parliamentary inquiry into this matter,” she said.

Claire O’Rourke, campaigns director at Solar Citizens, said the allegations are “truly shocking”.

“The Queensland government has at the same time waged an attack against rooftop solar, removing the guaranteed 8c feed-in tariff paid to owners of solar power systems and leaving people to negotiate directly with retailers over a price for the energy they produce,” she said.

“It is obviously very difficult for individual households to get a good deal from their power company. When retailers set the rules, solar owners lose.

“There needs to be a full and transparent investigation into the allegations made against Energex and the data used in its revenue proposal to the Australian Energy Regulator.”

Campbell Newman, the Queensland premier, has said that he wants to speak to Wilson about her allegations. He added that the Queensland Competition Authority is already looking at the issue of power prices and that the government wants “downward pressure” on bills.

The Australian Energy Regulator has told Fairfax it is aware of the allegations against Energex.