"Garden-grabbing" developers have won planning permission for 100 new dwellings every day within the gardens and grounds of existing houses. The figures will fuel the growing political row about the "overdevelopment" of tree-lined suburbs.
In some council areas, the figures suggest, up to 94 per cent of residential development is on gardens. "Garden-grabbing" has soared under new Government rules which make no distinction between gardens and "brownfield" sites.
Bob Neill, the Conservative planning spokesman, said: "There is now overwhelming evidence that Labour's planning rules are leading to leafy gardens being dug up, in turn being replaced with soulless and ugly blocks of flats or high density building crammed into the space. Ministers are in denial about these problems."
The figures come from councils' responses to a Government survey of 42 local authorities, covering a seventh of England's population.
The councils were a representative spread of rural, suburban and city authorities from across the country, making it possible to extrapolate an estimated England-wide total.
Findings of the survey, obtained under the Freedom of Information Act, show that between 2003 and 2008, the councils granted planning permission for 26,688 new homes on land which was previously occupied by houses and their front and back gardens.
The amount is a net total – for instance, if one large Edwardian house is replaced with a block of ten flats, it would count as nine new homes in the figures.
The survey totals equate to a figure of 186,000 new homes in England as a whole – 102 a day – or 210,000 for the UK.
Ministers have previously said that there is "no clear evidence of a problem" with garden grabbing, describing claims on the issue as "thin" and "anecdotal." However, the vast majority of councils in the survey said that it was an issue in their areas.
Among the worst affected were the London borough of Croydon, which saw almost 2,000 new homes built on the site of existing gardens and houses between 2003 and 2008, and the rural New Forest district, where the total over the same period was more than 1,500.
In its submission, Croydon council said that it was "particularly vulnerable" to the destruction of "cherished" back gardens and condemned planning policies as "ineffective." Neighbouring Bromley said garden grabbing was "a significant issue of concern for the borough" and "a retrograde step for a borough proud of its clean and green reputation."
Leeds council, although far less seriously affected than southern suburban authorities, called it "a significant issue and deeply unpopular in communities. It is known there are firms in the city scouring maps for spare land and approaching householders to get options."
Richmond-on-Thames, in south-west London, where more than a third of new homes are built on garden and house sites, said it was "a matter of considerable concern to the council and local communities."
Southampton, which gave permission for 1,220 such homes, called garden grabbing an "active threat to the character of mature suburbs, the heritage and biodiversity of the city" and said: "National guidance has made it difficult to resist development proposals on garden land. This imbalance needs to be rectified."
Garden grabbing accelerated under a new Whitehall "planning policy statement", PPS3, introduced by John Prescott, the then-deputy prime minister, in 2000. The statement – which all local councils must follow – required new higher-density developments in suburbs and defined gardens as brownfield land.
Previously-published Government figures show that the proportion of new dwellings built on "previously residential land" doubled between 1997 and 2008, from 11 to 23 per cent. However, these figures lump in developments on the site of existing houses and gardens with large-scale projects such as the demolition and rebuilding of entire council estates.
The new survey is the first which specifically aims to track, in the Government's words, "housing development on gardens".
Ministers say the rules are necessary to deliver the homes Britain needs. But critics say they are filling suburbs and villages with inappropriate "inner-city" development, destroying bird and wildlife habitats and increasing the risk of flooding.
Some councils, although hostile to garden development, say it is better than the alternative, building on the countryside. Chiltern district, where 89% of new development is on gardens, says it is a "very significant issue" in the area but without it "most of Chiltern's new housing would have to be delivered by release of green belt land".
A spokesman for the Department for Communities and Local Government said: "We have committed to consider action if the evidence discloses a problem, provided that a change of policy would not undermine our objectives on housing.
"Local authorities have the power to turn down applications for inappropriate housing development in back gardens and we expect them to use these powers where necessary.
“However, we recognise there are concerns over garden grabbing, which is why we’ve conducted a review looking at the impact of housing development on garden land, and we will be publishing our response shortly.”
Figures in your area
Council name New "garden-grab" homes (1) Percentage of all new homes delivered by "garden-grabbing" (2)
Basingstoke 560 19**
Bournemouth 611 7
Bromley 1411 11
Calderdale 815 12
Chichester 364 11
Chiltern 629 89
Craven 102 n/a
Croydon 1987 14
Derby 431* n/a
East Dorset 1056 94
Eastleigh 1012 n/a
Elmbridge 648 24
Fareham 1112 82
Guildford 209 7
Hertsmere 372 19
Leeds 843* 3*
Lichfield 338 19
Melton 245 14
Middlesbrough 114 3
New Forest 1510 46
North Dorset 238 32**
Poole 262 7
Richmond on Thames 360 36
Rotherham 265 4
Rutland 189 n/a
Sheffield 638 7
Solihull 992 31
South Tyneside 91 n/a
Southampton 1220 n/a
Staffs Moorlands 93 11
Sutton 1170 24
Swale 297 4
Three Rivers 230 45
Tonbridge & Malling 442 5
Warwick 447 2
Wakefield 1300* 17*
West Oxon 600 43
Windsor & M'head 449 18
Woking 530 33
Wokingham 1128 27
Wycombe 1148 24
Wyre Forest 230 12
(1) Total net new homes for which permission granted between 2003/4 and 2007/8. Includes refusals overturned on appeal, except * which do not include appeals.
(2) 2007/8, except ** which are 2006/7.