By Ron Bousso

LONDON (Reuters) - Top British North Sea producer Harbour Energy wants to sell stakes in North Sea oilfields and is reviving plans for a U.S. listing, sources said, as more firms scale back investments ahead of new tax increases on the sector.

The Labour government, which was elected in July, wants to use the revenue from oil and gas to raise funds for renewable energy projects. Finance Minister Rachel Reeves will announce the tax increases in her budget on Oct. 30.

The government is also preparing new environmental guidance for oil and gas projects, which executives said could further impede investments in the ageing basin, where output has declined by around 75% since its peak in the late 1990s.

Harbour has renewed its plans to acquire a U.S.-listed company that will allow it to list and move its headquarters to the United States, sources with knowledge of the matter said.

The search was paused when Harbour decided at the end of last year to acquire Wintershall Dea's non-Russian portfolio for $11 billion, the sources said. The deal, which allowed Harbour to diversify outside the North Sea and more than doubled its production, was completed last month.

Harbour has also launched a sale process of its stakes in the Armada, Everest, Lomond, Catcher and Tolmount fields as it seeks to reduce its exposure in the North Sea, the sources said.

Harbour declined to comment on the sale process, saying it was focused on the Wintershall Dea integration.

"We are a London listed company and as long as our geographical centre of gravity is in Europe it wouldn't really make sense to move the listing," a spokesperson said.

UN-INVESTIBLE

UK North Sea producers first warned they will reduce investments after the previous Conservative government introduced a 25% Energy Profits Levy (EPL) in May 2022 in the wake of soaring energy prices following Russia's invasion of Ukraine. The tax was subsequently increased to 35% in November 2022, and extended by one year in March 2024.

Britain's Labour government said it would increase the windfall to 38% from 35% starting Nov. 1, bringing the headline tax rate on oil and gas activities to 78%, among the highest in the world. Its duration will also be extended by a year to March 2030.

The changes will also include scrapping the levy's 29% investment allowance, which lets companies offset tax from capital that is re-invested.

"The UK (North Sea) is currently un-investible. Absent a sensible fiscal regime that encourages continued investments and provide some stability, it will continue to be un-investible," Serica Energy Chairman David Latin told Reuters.