The delay in the construction means that the commercial use of the reactor will probably not be ready for use until 2011.
According to the builders, the introduction of new security requirements is delaying the project. One of these is the requirement that the reactor building must be able to withstand the impact of an airplane crash.
Martin Landtman, the head of the project for TVO, said that the company is disappointed with the delay, but emphasises that achieving the level of security and quality is the most important consideration.
Greenpeace: "Come clean about safety!"
The environmental organisation Greenpeace said on Friday that contrary to previous claims, the planning for the new reactor does not meet the requirements set by Finnish law for security.
A Greenpeace spokesman noted that when the building permit was granted, it was claimed that it was designed to withstand a plane crash, a requirement which has been known to the planners since 2001.
Greenpeace called on TVO and the Radiation and Nuclear Safety Authority to issue a list of all quality and security problems linked with the reactor.