The millionaire paying Barnaby Joyce's rent runs a business that is benefiting financially from one of the Deputy Prime Minister's most contentious projects, the relocation of the Australian Pests and Veterinary Medicines Authority (APVMA).

Key points: Labor accuses Barnaby Joyce of breaching ministerial standards

Labor accuses Barnaby Joyce of breaching ministerial standards APVMA has spent $14,700 at the Quality Hotel Powerhouse, owned by Greg Maguire

APVMA has spent $14,700 at the Quality Hotel Powerhouse, owned by Greg Maguire APVMA invited almost 20 people to stay, wine and dine at Greg Maguire's hotel

Mr Joyce has defended allegations of pork-barrelling ever since he announced the $26 million plan to move the chemical regulator from Canberra to Armidale, in his own electorate.

The APVMA controls the relocation fund and so far, it has spent $14,700 at the Quality Hotel Powerhouse, which is owned by wealthy and influential New England businessman Greg Maguire.

Mr Maguire is a close friend of Mr Joyce, and the Deputy PM and his former staffer, Vikki Campion, are living rent-free in one of his apartments.

Mr Joyce defended that arrangement in Question Time this week, when Labor accused him of breaching ministerial standards.

The Opposition is also asking questions about whether Mr Maguire was awarded thousands of dollars in government contracts to host an agricultural function at his Armidale hotel last year.

Now, documents obtained by Saturday AM reveal another occasion when Mr Maguire's business benefited from taxpayer dollars.

The APVMA invited almost 20 people to stay, wine and dine at the Quality Hotel Powerhouse on April 26 last year.

An advisory committee, made up of APVMA and department of agriculture staff, as well as peak industry bodies, met at the hotel to work on the relocation plan.

There was a welcome dinner valued at almost $80 per head. On the menu were prawns with kimchi, truffle oil risotto, New England lamb and sticky date sponge.

The APVMA has not specified the total bill but a spokesperson said Mr Maguire's hotel is not the only one the regulator uses.

"APVMA staff have stayed at several accommodation providers in Armidale when travelling interstate for work. The Quality Hotel Powerhouse is one such accommodation provider," the spokesperson said.

"We do not have a preferred supplier. The Quality Hotel Powerhouse Hotel has been used as a meeting venue by the APVMA. As with travel, choice of meeting venues is determined by business requirements and is in line with relevant Government policies."

Revelation more fuel for Labor

As agriculture minister, Barnaby Joyce did not control how the APVMA spent its funds.

But the revelation is more fuel for Labor, as it continues its attack on Mr Joyce in the fallout from his affair with Ms Campion.

Shadow attorney-general Mark Dreyfus said it was "deeply suspicious" Mr Maguire ran a hotel that had benefitted financially from the regulator's relocation.

"This is another example of taxpayer funds, that ultimately Barnaby Joyce is responsible for, ending up in the pocket of a man who later gave him a very substantial gift," Mr Dreyfus said.

"It's the absolute duty of Barnaby Joyce, as a Commonwealth cabinet minister, to make sure there's not only no actual conflict of interest but the appearance of a conflict of interest is avoided."

The APVMA falls under the responsibility of the Agriculture Minister.

A spokesperson for the current minister, David Littleproud, said it would be misleading to suggest the Government encouraged or directed staff or agencies to use the Powerhouse Hotel.

"The APVMA chooses which venues it books for functions and each member of staff chooses where they stay using their travel allowance," the spokesperson said.

"Labor Party pollsters and many media organisations also chose to stay at the Powerhouse during last year's by-election."

The ABC contacted Greg Maguire for comment.