Planning Minister Nick Boles said just 9% of land is developed, and a surge in building of up to 3% will make huge strides in ensuring people are not priced out of the market.
The Conservative MP added people had to realise that good developments could be as attractive as open countryside.
Devon and Cornwall are blighted by social housing waiting lists and rocketing house prices that mean homes in attractive rural communities are as unaffordable as in London. But a series of developments have faced resistance from critics fearing the concreting over of the region's countryside.
In an interview with BBC's Newsnight due to be aired last night, Mr Boles says: "We're going to protect the greenbelt but if people want to have housing for their kids they have got to accept we need to build more on some open land."
He insisted everyone had "the right to live somewhere that is not just affordable but that is beautiful and has some green space nearby". That was "a basic moral right, like healthcare and education".
Westcountry MPs were last night wary. Andrew George, Liberal Democrat MP for St Ives, cautioned against a building a "developer's paradise". But Geoffrey Cox, Conservative MP for West Devon and Torridge, welcomed a relaxation of planning rules so long as it did not result in an "indiscriminate splurge".
Addressing so-called "Nimbys" – opponents to de velopment that argue "Not in my back yard" – Mr Boles said: "It's my job to make the arguments to these people that if they carry on writing letters their kids are never going to get a place with a garden to bring up their grandkids.
"I accept we haven't been able to persuade them. I think it would be easier if we could persuade them that the new development would be beautiful...
"The built environment can be more beautiful than nature and we shouldn't obsess about the fact that the only landscapes that are beautiful are open – sometimes buildings are better."
Mr Boles said he did not want "lazy" builders to build "pig ugly" houses, and urged them to work with local communities.
"Land is expensive but to some extent (developers) are just lazy," he said.
"They didn't talk to local people or get involved enough. But also it's just bloody expensive to build because land is expensive."
The Government faced stiff opposition when ministers proposed slashing more than 1,000 pages of planning policy to just 52, which they managed to get through after a series of compromises.
Ministers have also had to deny claims that they want to scrap the "green belt" – officially designated land ring-fenced from urban sprawl. Devon and Cornwall has no green belt, however.
St Ives MP Mr George said: "Cornwall has more than doubled its housing stock in the last 40 years but the housing problem has got worse.
"Nick Boles does not appear to have twigged that for some parts of the country simply building more houses is not the answer. We need clever development not just any development."
West Devon and Torridge MP Mr Cox said: "I support relaxing some of the planning laws in the countryside.
"The question is what the minister means. If what he wants is an indiscriminate splurge I would be extremely reluctant to see that. If he means a relaxation so that we can tackle housing shortages for people in rural communities and market towns I would support that. As ever with planning, the devil is in the detail."
Shaun Spiers, Campaign for the Protection of Rural England's chief executive, said: "Rather than giving up on good planning and allowing housebuilders to let rip, we should be re-using the tens of thousands of hectares of brownfield land available for high quality affordable housing, and strengthening protection for recognised 'tranquil' areas of countryside."
Hilary Benn, Labour's Shadow Secretary for Local Government, said: "We need to identify land for new homes, but it will be much harder to get that consent if communities feel they are being forced into accepting development."
