Trade Minister Tim Groser is defending his liquor bill from the Copenhagen climate change conference saying that over the eight-day stay it amounted to about two drinks a day.

And he said he was never inebriated on the job.

"I never get pissed when there is business to be done. Never. Never," he told the Herald yesterday.

The receipt from The Square Hotel in Copenhagen on his ministerial credit card bill lists various beverages including bourbon, The Famous Grouse whisky, gin, wine, Cognac, and Jim Beam.

He said his office had calculated that if all the alcohol was added up, it amounted to an average of 2.8 drinks per day - and if the cost of water was taken out as well it would be two drinks per day.

That figure included hospitality he offered to other people.

"Just as a matter of interest that is actually the definition that Alac uses for low-risk drinking.

"What people are trying to do is make a story about excessive drinking. I'm sorry, the facts don't fit it."

Mr Groser and members of a trade delegation were the subject of a complaint made public at the weekend about rowdy drinking on a flight back from Dubai in April.

"That's what's fuelling this," he said.

By his own account, Mr Groser spent quite a bit of time in his hotel.

"I never once negotiated at that conference. There was never a negotiation at ministerial level. I would wait up sometimes to four in the morning expecting a call to go up to the conference centre and it never came."

Mr Groser said the Copenhagen conference last December was "the worst conference I have ever attended". "The only public area in this strange little hotel was a bar by the reception. So yes a certain amount of drinking and discussion ... went on there but at the end of the day, when you add it all up it was 2.8 drinks per day for eight or nine days."

He also believed all his expenses were in the rules and that was the crucial thing.

"People can argue ... about what they would like the rules to be and that's the Prime Minister's judgment.

"But it is my understanding that absolutely [everything] on my receipts is squarely within the existing rules."

Speaking about the flight back from Dubai, Mr Groser said it had been "rowdy men".

"And for me personally it was the first time I allowed myself to start to come to terms with my mother's death, that I had heavily suppressed for obvious reasons."