Queensland’s deputy premier says he didn’t give special treatment to a quarry company, despite changes to river mining laws.

Queensland’s deputy premier has denied giving special treatment to a quarry business that had donated generously to the Liberal National Party.

Farmers at Harlin in southeast Queensland are upset that Karreman Quarries will have more scope to mine for sand and gravel in the Upper Brisbane River.

While the company had mined in the area for two decades, the ABC has revealed the Department of Natural Resources was considering legal action against Karreman.

Deputy Premier Jeff Seeney met with the company’s owner Dick Karreman in December.

Two months later, Mr Seeney asked bureaucrats to draw up retrospective special legislation after the department had ordered Karreman to stop extracting sand and gravel because it didn’t have the required permit, the ABC reports.

Amendments to the Water Act went through parliament without protest from the Labor opposition, enabling Karreman to quarry the lower bank of a river.

The laws were also backdated to 2010, with the deputy premier arguing he had opposed Labor’s changes to the Water Act four years ago.

Mr Seeney has denied any special treatment for the company, saying: “As shown by my dealings with Clive Palmer, everyone gets treated equally by our government and we deal with all issues based on the facts of the matter at the time.”

While farmers are adamant that quarrying is causing erosion on their land, Mr Seeney said that wasn’t necessarily the case.

“It’s also natural for people who are disaffected by that process to seek to point the finger at somebody to blame,” he told ABC Radio on Tuesday.

“We have to be very careful that we make sure that what’s happening in river systems all over Queensland isn’t used as an excuse to close down a business that’s been operating for 20 years.”

Karreman Quarries has donated $75,000 to the LNP in recent years, including a $1000 donation in 2010 to the local branch of backbencher Peter Dowling, who last year resigned as head of parliament’s ethics committee over a sexting scandal.

Lawyers for the company have told the ABC it rejects any suggestion it has operated outside the law, saying Karreman Quarries has always disputed the need for the state permit issued by the department.

The Lock The Gate Alliance has accused the government of favouring a major donor.

“This sort of government for mates, especially those in the resources sector, has not been seen to anything like this extent since the days of Sir Joh Bjelke-Petersen,” the group’s president Drew Hutton said in a statement.

The amendment was added onto reforms to the Water Act and wasn’t mentioned in the bill that preceded the vote.

Labor Leader Annastacia Palaszczuk said she knew nothing about it.

“The government needs to explain why they changed the legislation without telling anyone,” she told ABC radio.

“The onus is on the government to come and explain and also explain that massive donation that was given to the LNP.”

Labor’s environment spokeswoman Jackie Trad said the amendments were made “in the dead of night without any proper scrutiny”, and urged anyone with evidence of wrongdoing to contact the Crime and Misconduct Commission.

“What this indicates is a very worrying pattern of behaviour where there does appear to be preferential treatment given to those donors who make significant donations to the LNP,” she told reporters.

“If anyone has evidence, they should send it to the CMC.”

Environment Minister Andrew Powell said the amendments reversed reforms enacted under the previous Labor government in 2010.

Agriculture Minister John McVeigh said Labor’s legislation had caused impacts on companies like Karreman Quarries, which had operated within the law for 20 years.

“To change the definition of a water course … and expect that not to have an impact shows the Labor party doesn’t … understand economics,” he told reporters.

“They don’t understand regional business in Queensland.”