A record of the Thredbo Top station for 3am on Wednesday shows a temperature reading of -10.6C. This compares with the BoM's monthly highlights for June and July, both showing a low of -9.6C.

The BoM said it had taken immed­iate action to replace the Thredbo station after concerns were raised that very low temperatures were not making it onto the official record. Controversy has dogged the bureau's automatic weather station network since Goulburn man Lance Pigeon saw a -10.4C reading on the BoM's website on July 2 automatically adjust to -10C, then disappear.

Later independent monitoring of the Thredbo Top station by scientist Jennifer Marohasy showed a recording of -10.6C ­vanish from the record.

BoM initially claimed the adjustments were part of its quality control procedures. But bureau chief executive Andrew Johnson later told Environment Minister Josh­ Frydenberg that investigations had found a number of cold-weather stations were not “fit for purpose” and would be replaced.

The BoM has admitted that, in addition to Goulburn and Thredbo Top, stations at Tuggeranong in the ACT, Butlers Gorge and Fingal in Tasmania and Mount Baw Baw in Victoria would be replace­d.

An in-house investigation that includes two independent experts has been called. The bureau said it rejected allegations aired in some media outlets that it had sought to tamper with temperature data.

It has been reported online that electronic smart cards were allegedly fitted to the BoM's automatic weather stations, which put a limit on how low temperatures could be recorded in official weather data. The BoM declined to comment ahead of the internal review.

“The findings of a review into this matter will be made available after completion,” a BoM repre­sentative said. “We do not intend to publish detail prior to that.

“The AWS program is part of the observing systems and operations program, separate from the climate areas.”

On her website yesterday, Dr Marohasy said it was not the recording­ devices that were at fault. “To be clear, the problem is not with the equipment; all that needs to be done is for the smart-card readers to be removed,” Dr Marohasy said. (emphasis mine)