Homebuilder Larkfleet Homes is behind two outline applications for a respective 450 homes and 125 homes on adjoining sites at the village of South Wooton totalling 37 hectares.
Plans for the urban extension also include offices, open space, and a local centre with potential uses including a pub, shops and a community centre.
The proposed development is expected to achieve a density of 13 dwellings per hectare and provide 20 per cent affordable housing.
King's Lynn and West Norfolk Borough Council's planning committee members approved both applications yesterday.
According to a planning report, both sites form part of a wider development plan housing allocation for South Wootton which requires at least 300 dwellings to be provided on 40 hectares.
The report said that South Wootton and North Wootton parish councils had raised a series of objections to the applications, citing concerns about loss of greenfield land, lack of infrastructure, high densities, traffic impacts, and damage to local wildlife and habitats.
South Wootton Parish Council said the proposals, when considered alongside plans for another 700 homes at a nearby site, would increase the size of the village by 70 per cent.
Addressing concerns about the density of the larger of the two applications, officers said: "It is considered that the site can accommodate up to 450 dwellings without material harm to the visual amenity of the locality, highway safety or for any other technical reasons."
They concluded that "the general principle of this level of development on the site is considered acceptable" and said the "the proposal would ensure that the living conditions of existing and future residents would be protected from any materially detrimental impacts whilst providing much needed housing within the borough".
Officers also considered the likely impact of the proposals on nearby Natura 2000 sites - defined as Special Areas of Conservation and Special Protection Areas designated under the EU Habitats Directive and Birds Directive.
Nearby sites include the Roydon Common and Dersingham Bog Special Area of Conservation and The Wash and North Norfolk Coast Special Protection Area.
Officers concluded that proposed mitigation measures, including provision of open space and footpaths to reduce likely "increased recreation disturbance", would offer adequate protection and lead to "no likely significant effect" on the integrity of any European site.
In March this year, the High Court overturned a refusal of plans for up to 200 homes in North Norfolk after concluding that an inspector had overlooked the benefits of a proposed new school.
In September, Great Yarmouth Borough Council in Norfolk proposed slashing 2,000 homes from its local plan following publication of the government’s standard method for calculating housing need.
And in October, Breckland District Council in Norfolk voted not to support a proposed 10,000-home garden town due to concerns it would "jeopardise the integrity" of its emerging local plan.