The energy minister Michael Fallon has warned privately that fracking might soon face fierce resistance from the middle classes in Conservative heartlands as he heralded further exploration across swaths of southern England.

Fallon, a strong supporter of shale gas extraction, told a private meeting in Westminster: "We are going to see how thick their rectory walls are, whether they like the flaring at the end of the drive."

Fallon, who is MP for Sevenoaks in Kent, said exploratory studies for hydraulic fracturing – or fracking – were already poised to start in the north of England and were set to spread the length and breadth of southern England.

He said: "The second area being studied is the Weald. It's from Dorset all the way along through Hampshire, Sussex, East Sussex, West Sussex, all the way perhaps a bit into Surrey and even into my county of Kent. It's right there."

Fallon then referred to support for fracking among what he called the "commentariat" – newspaper opinion writers. "The beauty of that – please don't write this down – is that of course it's underneath the commentariat.

"All these people writing leaders saying 'Why don't they get on with shale?' – we are going to see how thick their rectory walls are, whether they like the flaring at the end of the drive."

Fracking experts have already admitted that the extraction method could result in flares several feet high as leaked gas is burned off rather than being allowed to leak into the atmosphere.

Charles Moore, biographer of Margaret Thatcher, lives in a £1.5m rectory in Etchingham, East Sussex, and has admitted that his support for shale gas extraction may conflict with his personal interests.

Moore wrote last month that shale gas was "a great advance" though it was lucky that much was in the north where there were "not many spoilt rich people to complain".

But he added that there was said to be "lots more under the Sussex Weald where I live" and he faced having to be "true to my beliefs".

Drilling for oil close to the West Sussex village of Balcombe has begun after a week of blockades and protests by both villagers and anti-fracking activists.

Fallon has said in public that fracking will not damage the countryside. "Claims that exploration involves ruining the countryside are nonsense," he said. "A typical shale gas pad is expected to be little larger than a cricket ground."

He said he had visited a conventional drilling site "tucked away in the South Downs national park, which shows how oil and gas operations can work even in the most sensitive environment".

Fallon conceded that there was bound to be some disruption but said this could be overcome with compensation of £100,000 for each exploratory well site.

The concern for the Tories is that they are about to find themselves pitted against their rural base again, as they have been over windfarms, planning laws and the High Speed 2 rail line.

But Fallon has said that in the US, where the fracking industry is well advanced, "there is no evidence of fracking causing any groundwater contamination".

Energy companies are only being authorised to search for the possible location of shale gas – not to exploit it. But ministers are preparing generous compensation to overcome resistance as they have for wind farms and nuclear power stations.

In his private briefing at Westminster, reported in the Mail on Sunday, Fallon stressed that local communities affected by fracking would be rewarded with generous royalties in the form of compensation to improve local facilities.

He said: "If that is between five and 10m quid and there are 20 wells in your area, the local area and the immediate residents will benefit substantially."

Fallon said it was time to "get on" with fracking. "We now know there is probably twice as much shale in the north as we originally thought.

"It looks as if there's much more shale gas here than anybody realised and it looks as if the shale is thicker than the shale in the US where there have been dramatic reductions in people's gas bills and in the cost of energy for business.

"What we don't yet know is whether we can get it out as efficiently and cheaply as they have been able to in the States and that is the purpose of these studies.

"We are sitting on all this shale. We owe it to the next generation to go down there, let these companies go down there and find out whether we can extract it and whether this is a new, large source of cheap energy."

The official estimate is that the UK has 37 trillion cubic metres of shale gas in the north of England; geologists have yet to quantify reserves in the south.

Polling for the Sunday Times by YouGov shows quite strong support for fracking so long as it is part of an energy mix.

But the Liberal Democrat president, Tim Farron, put himself at the helm of those in the coalition concerned at the pace with which the government is moving. He said: "I am afraid the government has seen flashing pound signs, and has not considered the long-term threats fracking poses to the countryside.

"I think this is a very short-sighted policy, and we will all be left to live with the consequences. With a wind farm you can actually choose where you put it; that is not the case with fracking.

"This technology can lead to earth tremors and I'm particularly worried that buried nuclear waste in my part of the country could be affected. We should be investing more in renewable fuels.

"I am very sceptical. The green movement were pro wind farms, and countryside groups were against. With fracking you are already seeing powerful alliances forming between those two groups, so opposition could become very strong."

Don Foster, the Liberal Democrat communities minister, warned there could be danger from fracking in his Bath constituency since it would take place very close to the water tables that supply the city.

Foster said his Lib Dem colleague the energy secretary Ed Davey was taking a proportionate, cautious approach: "There is a potential for significant benefit to our energy security but because of environmental concerns we are doing it in a very careful way."

Craig Bennett, director of of Friends of the Earth's policy and campaigns, said: "Michael Fallon's unguarded comments will resonate across the UK and fuel more opposition to the government's disastrous support for fracking.

"Ministers must pull the plug on shale gas and oil extraction, especially as there's plenty of evidence they won't lead to cheaper fuel bills.

"We need an energy policy based on cutting waste and developing the nation's huge renewable power potential – not one that wrecks our clean and pleasant land and pumps more pollution into our atmosphere."