Norway's centre-left government said on Wednesday it plans to increase taxes on electricity producers and fish farmers to raise an extra 33 billion crowns ($3 billion) a year.

"Energy producers and the aquaculture industry make billions of crowns on our common resources," the finance ministry said in a statement. "The government is now proposing that more of the value created should go back to society."

Shares in fish farmers such as Mowi, the world's largest, Leroy Seafood and SalMar fell on the news and were down between 15% and 19% at 0719 GMT, underperforming an Oslo benchmark index which was 3.4% lower.

While Norway has a $1.2 trillion sovereign wealth fund, the world's largest, the government says it plans to cut spending from the fund next year in order to curb inflation.

The extra taxes impose a resource rent tax on aquaculture and wind power, an increase in the resource rent tax on hydropower and an extraordinary tax on wind and hydropower due to the very high electricity prices.

Costs linked to taking in refugees, ongoing public construction projects, benefit payments and household power subsidies will rise by some 100 billion crowns in 2023, the government has said.

"In reality, we have two ways to close this gap: major cuts in welfare such as pensions, health, police and care for the elderly, or through tax increases," said Finance Minister Trygve Slagsvold Vedum, who is from the rural-focused Centre Party. ($1 = 10.8822 Norwegian crowns) (Reporting by Terje Solsvik; Editing by Gwladys Fouche and Alexander Smith)