Cluttons calculates that planning consent has been granted for more than 2.85 million sf of new development in the area. This is the equivalent of more than three years' take-up at current levels. And on top of this planning applications have been lodged for another 1.6 million sf, primarily in Irvine Sellar's controversial 1,000-ft tower at London Bridge Station. Construction activity is already high with over 650,000 sf currently underway.

At the same time Cluttons' research points to weakening demand, which in turn has led to increased availability and falling prime rental values. Total available space has increased by 33% to 386,643 sf since the Spring as demand has tailed off. And top rental values have fallen back from £45 ($66) per sf earlier in the year and now stand at £40 ($58) per sf.

Melanie Bayliff, research analyst in Cluttons' Central London business team said: 'There is a real risk of oversupply in the next 2-3 years if all of the schemes in the development pipeline go ahead. However, we believe it is more likely that some schemes will either be postponed or abandoned to avoid such a situation.'