A row over an old nuclear reactor site that was fully decommissioned over 20 years ago threatens to delay regeneration work in the Lower Lea Valley.

The row centres on the failure to disclose the ex-nuclear site to the International Olympic Committee (IOC) but a new survey could delay regeneration of the area. A Conservative member of the London Assembly who made details of the reactor public called for a fresh survey of the site, threatening plans to get on with the redevelopment of the site, part of the Olympic Stadium area.

However, London 2012 officials have insisted there is no health and the site is clean. Queen Mary College’s department of nuclear engineering who built the reactor in 1980 issued a statement declaring that the reactor was closed down in 1982, under supervision by the Nuclear Installations Inspectorate, and that there were "absolutely no ongoing health implications of the decommissioned reactor."

"The reactor was exceptionally small; the core was the size of a bucket and produced virtually no energy," the college said in a statement.

Bob Blackman, the Tory economic development spokesman, said: "During this process, officers at the bid team have been very blasé about the problems of contamination in the Lower Lea Valley, but they must take this matter seriously."

"We have got a huge amount of building to do and this work cannot even start until we clean the site up."

A spokesman for the London Development Agency said: "This seems to be completely spurious. There is no issue here because it was fully decontaminated 23 years ago. It is not relevant what was there years ago if there are no health implications now. There was a full process of checking everything in the area."