Major residential schemes, including those earmarked for the Thames Gateway, could be torpedoed under new Environment Agency (EA) powers, it has emerged.
Mandarins at the agency have been given unprecedented authority to veto projects planned in areas at risk of ooding - a move which has already scuppered a number of projects around the UK.
Under new government rules, contained in Planning Policy Statement 25 (PPS25), the EA can for the first time block housing applications even if they win local council support.
The policy has worrying implications for Thames Gateway regeneration, where more than 90 per cent of development land lies in designated flood-risk areas.
Around 160,000 houses and ats are planned for 2016, stretching from the capital along the Thames estuary.
Dan Stainer-Hutchins Architects (DSH) is one of the first practices to feel the force of the EA's new punch. The Gloucestershire-based practice has been forced to scrap a 16-home development in the county and the developer - unnamed - is unwilling to fight the decision.
Dan Stainer-Hutchins, managing director of DSH, said: 'We came up with conventional and exotic solutions but the developer gave up. This has the potential to disrupt hundreds of residential schemes across the whole UK.'
A DSH apartment scheme in Cardiff has also been blocked unless ground- oor ats are redesigned as offices or shops.
Stainer-Hutchins said: 'Our client has been forced to delete ats. One way round the policy is to put the ats over commercial premises. It seems you can drown at your desk but not in your bed.'
'Applications going through at the moment will be hammered if the kind of summary treatment we endured is anything to go by.'
The Association of Consultant Architects echoes Stainer-Hutchins' concerns.
Planning group head Andrew Rogers said: 'This has the potential to disrupt residential and indeed commercial projects around the UK. It will also put greater pressure on planning resources.
'But the main issue is that developers will have to weigh up whether a project is viable.
There is a very fine balance between the economic situation and a project's limitations.'
And Jon Robinson, principal of engineering consultancy Scott Wilson, which is working in the Thames Gateway, said: 'There are a number of Thames Gateway developments that may now come under renewed scrutiny by PPS25, but we welcome PPS25 because it encourages an holistic view of ood risk planning.'
Naturally, the EA has defended its new powers.
Mark Southgate, head of planning and environmental assessment, said: 'Flooding is one of the most serious material considerations in planning.
Properly located and planned developments can minimise ood risk, and in some cases even reduce it for others in the vicinity.'