Lawyers warn that developments could face expensive delays after the European Court of Justice rules that a local authority was wrong not to require an environmental impact assessment.
Lawyers have warned that developments could be hit by delays and millions of pounds of costs after the European Court of Justice ruled that an environmental directive had been incorrectly interpreted in the UK.
Last week the court ruled that a local authority had been wrong not to require a developer to conduct an environmental impact assessment.
Until this ruling UK law stated that these assessments, which evaluate "all significant effects" a scheme has on the environment, such as pollution and noise, are only required at the outline planning stage.
Environmental campaigners in the case of Barker vs London Borough of Bromley argued that this was unfair because developers could change their schemes at the "reserved matters" stage, the next step in the planning process, without having to consider the environmental impact.
The ruling means that assessments could be requested at any stage in the planning process, not just the outline stage.
The row originated in 1999 when Bromley council gave planning permission for a multi-screen cinema in Crystal Palace Park without requesting an assessment, despite concerns about environmental damage.
Lawyers said the ruling threw up another procedural obstacle for developers, which environmental campaigners would use to delay or halt schemes they opposed.
Duncan Field, planning partner at SJ Berwin, said: "The professional costs of carrying out an assessment can run into millions and preparing it could take up to 12 months."
Delays could be even longer where the impact on wildlife has to be considered because surveys may have to be done at a particular time of year, for example where sites are known for having nesting or migratory birds.
Field said such delays would cut into profit margins because developers may miss opportunities in the market.
Tony Kitson, a planning partner at Cameron McKenna, said: "The ruling is of particular concern for speculative developments where the detail may not be known at outline planning stage because the tenants may come along with particular requirements later on."
Although the cinema scheme was abandoned in 2001, the Crystal Palace Campaign took its case to the House of Lords. It was then referred it to the European courts to decide whether UK law complied with the European directive.
It is expected that the Barker case will go back to the House of Lords for a decision in the autumn and that the UK government will amend the environmental impact assessment regulations in the next six months.