OSLO, Aug 30 (Reuters) - A new government in Norway would seek to overturn a cut in natural gas pipeline tariffs that has prompted threats of legal action from some of the pipeline owners, a leading contender to the post of oil minister told Reuters on Friday.
In June, the Nordic country - the world's third-biggest gas exporter and Britain's top gas supplier - went ahead with plans to cut the tariffs that pipeline owners can charge energy firms for transporting the gas from North Sea oil platforms to processing plants onshore and European markets.
The new tariffs are set to become effective from 2016.
The pipeline owners say the move would cost them $6.6 billion in lost earnings over the next two decades.
These investors, including the Abu Dhabi Investment Authority, German insurer Allianz, Swiss bank UBS and France's Caisse des Depots, have spent $5.1 billion in recent years buying stakes in Norway's gas pipeline infrastructure, called Gassled, which manages 8,000 kilometres (5,000 miles) of pipelines.
The tariff cut was pushed through by a Labour-led coalition widely expected to lose elections on Sept. 9. If that happens, a new governing coalition could include the centre-right Conservatives and the populist Progress Party.
"We will go back to the Gassled tariffs that used to be," Ketil Solvik-Olsen, the Progress Party's finance spokesman, told Reuters.
"I think that what they (the government) have done with the Gassled tariffs and with the oil taxes is hurting the predictability of Norwegian politics."
Solvik-Olsen said tariffs could be changed for future projects, but not retroactively for existing projects.
"You can't sell things where people assume high prices in the future and as soon as the sale is done you decrease the rates," said Solvik-Olsen, who is a leading - but not the only - contender to run the key oil and energy ministry.
The change would be one of several adjustments the Progress Party would like to make to decisions regarding the oil sector taken by the current government.
In May, Norway lowered the amount that energy firms can write down on their investments.
"We would like to overturn the oil tax hike. We would want a white paper on oil tax. The changes are not well thought out," Solvik-Olsen told Reuters earlier this month.
Solvik-Olsen's Progress party is unlikely to be the dominant party in a future government and would have to work with the Conservatives, who have not commented on their possible stance in this case.
The Gassled case is closely followed by infrastructure funds and energy investors worldwide since a stable and predictable regulatory framework is one of the most important elements in a sector that immobilises large amounts of capital over long periods of time. (Editing by Tom Pfeiffer)