Power price hikes by the State Government appear to be biting with bad household debts written off by electricity provider Synergy more than doubling in two years.

After successive bill increases amounting to almost 20 per cent since July last year, the number of residential customers whose overdue accounts have been forgiven by Synergy has risen to 30,355 compared with 16,540 in 2015-16.

At the same time, the value of unpaid household bills written off by the State-owned utility has increased from $8.1 million two years ago to $17.5 million in the 12 months to June 30.

The figures were revealed after questioning by the Opposition in Parliament over concerns about the effect the power price rises were having on vulnerable customers.

Sources said bad debts could be caused by a range of factors including an inability to pay, customers skipping town, households with multiple tenants gaming the system and phantom accounts in false names.

Energy Minister Ben Wyatt said any time “negative” trends were reported it was concerning but he stressed that it was often difficult to determine why a customer’s debt was written off.

Mr Wyatt also noted that utilities such as Synergy had to follow an “exhaustive process”, including trying to contact customers before they could disconnect someone or cancel a debt.

“It is always concerning when we see negative data, however, by their very nature when debts are written off the customer has stopped engaging with Synergy,” he said. “The Liberal Party is merely assuming a reason for its own political gain rather than having any accurate insight into the issue.”

Synergy said there were many reasons why customers fell into arrears including financial difficulty. However, a spokeswoman said “there is no specific evidence suggesting an increase in written-off debt can be directly attributed to any single factor”.

She also said there had been no material change to the way Synergy assessed bad debts since 2014.

“There are many reasons why customer accounts may be overdue/outstanding, including if they are experiencing genuine difficulty in being able to pay amounts owed,” she said.

“Synergy uses its best endeavours to recover outstanding monies but is unable to determine the exact motivations of any former customer who does not want to reconcile their accounts and refuse to engage with Synergy.”

Shadow energy minister Dean Nalder said the jump in debt write-offs reflected the cost-of-living increases imposed by the Government and curbs to hardship assistance brought down by Mr Wyatt last year.

“The more than doubling of debts written off by Synergy over the last two years is another demonstration of the significant impact the McGowan Government’s $700 increase in fees and charges is having on struggling households,” he said.