A Japanese ambassador has joined the campaign against Queensland coal royalty hike.

Japanese ambassador Shingo Yamagami has emerged as a vocal critic of the Palaszczuk government’s decision in June to create a tiered royalty rate and cash in on record coal prices driven by Russia’s invasion of Ukraine.

The new royalty regime is on track to net the Queensland government up to $6.4 billion more this financial year than it would have under the state’s previous royalty regime.

Mr Yamagami spoke at the launch of the Queensland Resource Council’s $40 million marketing campaign against the new coal royalty regime at its annual forum in Brisbane.

Japanese firms such as Mitsui and Mitsubishi have major coal investments in Queensland.

The ambassador warned that Japanese companies may reconsider joint ventures in hydrogen and other sectors if the situation is not resolved.

“Japanese coal companies are yet to see any glimmer of hope that the situation will improve,” Mr Yamagami said.

“Alongside coal, Japanese investment and trade in Australian gas is a cornerstone of our partnership based on trust.”

Mr Yamagami has told reporters that the Japanese government does not support or oppose any party in any domestic political debate in Australia, leaving policy “entirely up to the Australian people and Australian political leaders”.

“Regarding the Queensland coal royalty, we have been communicating to the relevant authorities the concerns of Japanese businesses operating in Australia to the effect that they were not properly consulted prior to the announcement of the measures, and that the decision could damage the trust in Queensland and beyond as a safe and predictable place to invest,” he said.