* Shippers fight $2.3 bln back-tax claim in court
* Shippers say new tonnage tax hurts Norway's reputation
* Finance Ministry says new rules helping shippers return
By Aasa Christine Stoltz
OSLO, June 3 (Reuters) - Norway's government meets two shipping companies in court on Wednesday to defend its tonnage tax that imposes a big tax bill on the industry at a time when the global downturn is hammering profits.
A scheme presented in 2007 aims to make Norway's system similar to tonnage tax systems in countries of the European Union, of which Norway is not a member. It also imposes 14 billion crowns ($2.3 billion) in back taxes on undistributed profits retained by shippers over many years.
The shipping industry has clashed with the Labour-led government, calling the new tax a betrayal of a 1996 deal meant to keep them competitive under the Norwegian flag, and many say Norway's reputation as a maritime nation has taken a hit.
If the companies -- three so far -- win in court, it could set a precedent for many others.
The Nordic country with its long stretch of coastline has been a major player in shipping for 150 years and controls about 5 percent of the world's merchant fleet.
Norwegian groups have so far paid 2.8 billion crowns of the bill but are seeking to reverse the back tax in full, claiming it is illegal as no laws should have retroactive effect.
"Our main argument is that we have been charged back tax overnight from the last 11 years, and we believe this is in violation of ... the constitution," Jan Haakon Pettersen, chief executive of energy shipper BW Gas, told Reuters.
NOT AS BENEFICIAL
The government argues the old system gave the shipping industry a postponement of taxes, not an exemption.
BW Gas, controlled by the Hong Kong-based Sohmen family, has been hit with a total bill of 3.9 billion crowns and is one of those due to meet the government in court. Farstad Shipping will also start its case in court the same day.
The industry's old tax system was not as beneficial as in other European countries, which has already led companies such as oil tanker group Frontline to move its headquarters out of the country -- in this case to Bermuda.
BW Gas said it was working to move the "centre of gravity" of its business out of Norway due to the imposed tax, while maritime industry group Wilh. Wilhelmsen responded to the plan by moving its shipping activities to Malta.
Many shippers believe the reputation of Norwegian shipping and the North Sea country's general business climate has been hurt because the international industry frowns upon the tax.
"This has hurt Norway's reputation, there is no doubt about that," Pettersen at BW Gas said. "For shipping, I would say it has been particularly damaging."
Deputy Finance Minister Geir Axelsen disagreed. "We see tendencies that ship owners are coming home because they view the tonnage tax system as attractive after the changes we made in 2007," Axelsen told Reuters.
The case is expected to go all the way to the supreme court, according to those involved, and possibly further to the EU court system, if necessary. (Editing by David Holmes) ($1=6.198 Norwegian Crown)