Another at-risk customer – whose premium rose nearly 700 per cent – tells the same story. NRMA Insurance denies wrongdoing in that case. More on that later.

First, to Goulburn, where Maree Burns’s premium on $80,000 of contents has gone from $265 to $864. That’s a 226 per cent jump.

Blog with Public Defender John Rolfe

When an NRMA Insurance representative called Ms Burns he said the jump was due to a new council survey.

But Goulburn Mulwaree Council general manger Chris Berry told Public Defender it had not changed flood mapping for at least two years and the most recent survey was in 2005.

An NRMA Insurance spokeswoman conceded: “It’s human error. We placed far too much emphasis on a council flood study.”

She added that the flood insurance call centre team would be counselled over Ms Burns’ case.

Ms Burns said: “It’s a rort.”

She is looking for a new insurer, with Public Defender’s assistance.

AAMI said it could provide a higher level of cover for less than half NRMA’s charge.

Mr Berry said Goulburn experienced a one-in-50-years flood earlier this month.

It didn’t come anywhere near Ms Burns’s place.

Adrian Byrnes not only has a similar surname to Ms Burns, he has a similar story.

The difference is, the size of the increase Mr Byrnes faces is even bigger – a staggering 680 per cent.

And in his case, NRMA claims it really did receive fresh council information.

Mr Byrnes had been paying about $540 a year to cover $110,000 of contents at his Windsor property. That is set to rise to more than $3600.

“We are in a one-in-100-year flood area. We knew that when we bought here in 2010,” Mr Byrnes said.

“We told NRMA. They said it was no issue.”

Then, a week ago, an NRMA rep called to reveal the hike and claimed it was due to new flood data from Hawkesbury Council. The NRMA spokeswoman yesterday backed the rep, saying Hawkesbury Council had supplied fresh information.

Council general manager Peter Jackson said it had not.

As with Ms Burns, recent persistent heavy rains did not imperil Mr Byrnes’s home.

A quick Google search revealed NRMA has also sprung steep increases on supposedly flood-prone customers in Canberra, Penrith and Coffs Harbour. Three weeks ago the owner of the NRMA Insurance brand, IAG, revealed its premium revenue had grown faster than investors expected – and would keep doing so. Since then its shares have risen 18 per cent, adding about $1 billion to company’s worth.