Anti-mining protesters arrested at rally

Two protesters have abseiled off a balcony outside a luxury hotel in Sydney's CBD and unfurled an anti-coal seam gas mining banner.

The stunt at lunchtime came after a group of about 16 activists gatecrashed the NSW Minerals Exploration and Investment conference inside the Sofitel Wentworth Sydney hotel on Thursday.

They lined up in front of the stage, holding up anti coal seam gas banners and trading insults with the gathering, until police intervened.

About 50 farmers and people from rural communities stood across the street from the hotel to take part in a rally at 12pm (AEST).

Greens councillor Max Phillips said mining companies had been granted licences to conduct coal seam gas exploration across as much as 25 per cent of the state.

"It's widespread," he told AAP.

"From Casino and the northern rivers through to Moree Plains, the Pilliga, Liverpool Plains, down the Hunter."

Approval had also been given for coal seam gas exploration in the Illawarra escarpment, Camden and Sydney, he added.

Farmer Ted Finnie said oil and gas exploration company Santos had been granted a licence on his 576 hectare property on the Merriwa Plateau in the Upper Hunter.

But there's no way he will agree to coal seam gas mining.

"They are certainly indicating they will be drilling but they will not be getting onto my place," Mr Finnie said.

"Over my dead body."

Rosemary Nankivell from Liverpool Plains said the physical impacts of coal seam gas mining included ground water depletion and contamination of aquifers.

She visited Santos chairman Peter Coates in February.

"We asked them to give us a written guarantee, that they would not impact on the farming activities of the Liverpool Plains and our water resources underneath," she told the rally.

"We are still waiting."

During the speeches, a man and a woman dressed in a business suit, climbed over the balcony of the Sofitel Wentworth Hotel and unfurled a banner emblazoned with a large stop sign and the words: "Enough is Enough: Stop coal and gas expansion".

A police rescue van pulled up with a ladder and an officer attempted to coax the pair down a short time later.

They avoided him by climbing back up to the balcony, only to be met by several police officers who arrested them.