Ministers have changed planning rules for the countryside to favour "innovative cutting-edge designs" over traditional country house styles.
Rural Britain: Cutting-edge makeover?
Planning minister Keith Hill said he wanted the best British architects to design country houses "that our future generations will be proud of".
The change was welcomed by the Royal Institute of British Architects (RIBA).
The Tories highlighted other changes in the planning guidance which they say weakens protection of farmland.
Planning Policy Statement 7 replaces "Gummer's Law" - Tory environment minister's John Gummer relaxation of planning guidance to allow traditional houses to be built in the countryside.
That has now been changed to allowing new houses in the countryside which "reflect the highest standards of contemporary architecture".
Mr Hill said: "Not only do we hope that cutting-edge designs for country houses will raise the standards of rural housing more widely, we also expect them to leave a legacy from today's top architects for the history books of the future."
President of RIBA, George Ferguson, said: "This clause is greatly welcomed, and is a brave and vital endorsement by government of the value of excellence in design.
"The country house through the ages been one of the defining elements of our architecture and social history. It has embraced all styles and types and should continue to be characterised by its excellence rather than an adherence to any one architectural movement."
The "Country House Exception" in the new planning statement says: "Very occasionally the exceptional quality and innovative nature of the design of a proposed, isolated new house may provide this special justification for granting planning permission."
It goes on to say "the value of such a building will be found in its reflection of the highest standards in contemporary architecture, the significant enhancement of its immediate setting and its sensitivity to the defining characteristics of the local area".
The planning policy statement is for local authorities to use in judging planning applications.
It continues to protect National Parks and Areas of Outstanding Natural Beauty and retains Local Landscape Designations "where there is clear and robust justification for doing so".
It says most rural development should be on previously developed land in existing towns and villages.
Mr Hill said: "It's vital that our rural communities have the homes, facilities and services to allow their economies to grow. A blanket ban on all development in the countryside would stifle the local economy and could prove disastrous for farmers and rural-based enterprises.
"We need to support and breathe life into our rural communities so they are thriving and prosperous. But we must also ensure that planning plays its part in protecting the wider countryside from unnecessary development so that its natural beauty, heritage, and wildlife can be enjoyed by all."
A Council for the Protection of Rural England spokesman said the new guidance "significantly weakened" the protection of good quality agricultural land.
It was "fundamentally wrong" that the government was now telling planning authorities to consider the need to protect good quality agricultural land alongside the need for the accessibility to infrastructure, workforce and markets he added.
Caroline Spelman, for the Tories, said: "We already knew that John Prescott was planning to let rip with his bulldozer over England's Green Belt.
"Now he has England's farmland in his sights, by weakening local councils' ability to protect their communities from unsustainable and unwanted development.
"Downgrading the protection of farmland will open the floodgates for a barrage of attempts by developers to cover some of our most beautiful and valuable countryside with concrete.
"Labour just want to mitigate for their failure to stop the rural depression in agriculture by bulldozing what's left of it.
"The Government should address the causes of the crisis in the agricultural economy and focus on promoting brownfield development and the regeneration of our market towns."