Joyce spoke up for electorate: PM

Tony Abbott says his agriculture minister was merely giving voice to the feelings of his electorate when he criticised a new mine in his area.

Tony Abbott has excused Barnaby Joyce's outburst over a $1 billion mine approval in his electorate. (AAP)

Prime Minister Tony Abbott is playing down a rift with one of his cabinet ministers who declared the "world has gone mad" after the government approved a $1 billion coal mine.

Barnaby Joyce is outraged the federal government granted Chinese company Shenhua approval for the Watermark mine in his NSW electorate, labelling the decision ridiculous.

But Mr Abbott excused the outburst as merely Mr Joyce wearing his local member hat and giving voice to the many disappointed constituents in his electorate.

"We're all local members first".

"We're all local members first," the prime minister told reporters in Grafton on Thursday.

"Sometimes as a local member you've got to give voice to the feelings of your constituents while at the same time being a loyal member of the government."

Mr Abbott is familiar with his minister's predicament and compared his opposition with the Howard government placing mobile phone towers in his electorate. "I was very hostile to them," he said.

The approval could be a motivator for a political comeback from former independent MP Tony Windsor, who previously held Mr Joyce's seat. Mr Windsor is considering trying to win a place back in the federal parliament and his interest in the mine could be the extra push he needs to stand.

The mine, near Gunnedah, is subject to 18 conditions the government says are some of the strictest in history.

But on Wednesday night Mr Joyce took to his Facebook page to complain about the approval, which he's long opposed.

"I think it is ridiculous that you would have a major mine in the midst of Australia's best agricultural land".

"I think it is ridiculous that you would have a major mine in the midst of Australia's best agricultural land," he wrote.

"I think the world has gone mad when apparently you cannot build a house at Moore Creek ... but you can build a super mine in the middle of the Breeza plains."

On Thursday Mr Abbott defended the approval made by his environment minister Greg Hunt, saying he believes it's possible for high-quality agriculture and mining to coexist.

"It's a mine in the hill country, it's not a mine that is on prime agricultural land," he said. "(But) I can understand why local people are very concerned to protect their environment."

Mr Joyce wasn't with the prime minister at his Thursday press event, despite it being held near his electorate and focusing on his portfolio.

His office told AAP the minister was unable to change his schedule to make the event and Mr Abbott later dismissed suggestions the pair were intentionally trying to avoid each other.

"Look, nothing gives me greater pleasure than to be on the hustings with Barnaby," the prime minister said.

The Greens accused the government of putting overseas mining interests before local farmers and the climate, and accused Mr Joyce of failing to protect the Liverpool Plains.