Fears have been raised about a surge in so-called 'garden grabbing' after Angela Rayner overhauled planning rules.
The Communities Secretary has relaxed restrictions on building new homes in the gardens of other houses.
The update means limits on the size and appearance of homes built in gardens could be circumvented.
The developments previously needed to 'be consistent with the overall street scene', but this can now be overruled in some circumstances. This includes cases where it is 'appropriate to have larger buildings', such as on street corners.
New homes can also take up over half the former garden size – as long as they can be 'accommodated without harm to the overall character of the area'. They can be twice the footprint of all the existing buildings on the site.
Such projects would still be subject to the full planning process and depend on adequate local infrastructure being in place.
Angela Rayner with Andy Burnham... the Communities Secretary has relaxed restrictions on building new homes on existing plots as Labour tries to meet home-building targets
The updated National Planning Policy Framework – which sets out guidelines councils should follow when deciding whether to approve or reject applications – has taken effect as Labour desperately tries to meet its target of constructing 1.5million new homes by 2029.
A Ministry of Housing, Communities and Local Government spokesman said: 'We have made changes which recognise that in many places, there is potential for more development, to support thriving neighbourhoods, improve access to jobs and services, and make the best use of land within our towns and cities.
'Our changes will help more homes be built where they are needed, while stopping unsuitable development.
'Local people will still be able to have their say, and councils must take those views into account.'
Shadow housing secretary Sir James Cleverly said Labour was carrying out a 'power grab' and launching a 'new campaign of garden grabbing' because building was falling short. The Government announced yesterday that mayors are to get powers to bulldoze through major housing developments.
The local leaders will be able to overrule councils to approve significant building projects – or block them.
As well as 'calling in' decisions made by authorities, mayors will be allowed to grant upfront permission so developers do not even need to apply.
Critics have warned that the changes make it more likely that objections from residents will be ignored.