The Queensland Government has decreased new land valuations on properties near a contaminated aviation base.

Residents living near the Oakey Aviation Base have been unable to use or build on their land after groundwater was found to be contaminated by toxic fire-fighting chemicals PFOS and PFOA.

But around 30 properties in the contamination zone recently had their valuations increased by the state's valuer-general.

It meant that many were slugged with higher council rates, despite private appraisers deeming some blocks “worthless”.

After strong public backlash, valuer-general Neil Bray has now reduced the value of 28 properties.

“Oakey property owners who lodged an objection to their 2016 land valuation were notified of the outcome of the State Valuation Service's review,” Mr Bray told the ABC.

“This review included consideration of other land valuations in the Oakey area and led to reductions in valuations for a total of 28 properties.

“The reductions were made taking into account the specific grounds raised in the individual objections as well as consideration of comparative land valuations.”

But letters sent to residents whose valuation decreased said the reduction would not necessarily mean that Toowoomba Regional Council would charge lower rates.