Barnaby Joyce has declined a $40,000 prize that mining magnate Gina Rinehart sought to give him for his agricultural efforts.
Ms Rinehart presented the award and the cheque at an event on Tuesday to honour the former deputy prime minister's leadership in the agriculture industry.
However, Mr Joyce has declined the money.
"I was very humbled to receive the award but very surprised to receive the novelty-sized cheque. I did not take any cheque from the event and as soon as office hours resumed today, I took immediate action to politely decline any acceptance," he tweeted on Tuesday.
Opposition Leader Bill Shorten said the incident was "unusual and concerning".
"Barnaby Joyce, what on earth are you doing accepting $40,000? And I have to say, why is a mining millionaire giving a Turnbull government minister a $40,000 cash present?" Mr Shorten told reporters in Brisbane on Wednesday.
"This is very unhealthy for our democracy. It's not right. It doesn't look right, it doesn't smell right."
Mr Joyce, the Nationals leader and former agriculture and water minister, is fighting a by-election in New England after falling foul of the constitution over his dual citizenship.
The National Farmers Federation has distanced itself from the award.
"NFF didn't, don't & won't support such awards," chief executive Tony Mahar tweeted.
