Profits from North Sea oil and gas may be far lower than the government’s prediction, putting a planned investment in rail infrastructure at risk.

In March, the government announced that it was harmonising the taxation rules for North Sea oil companies in a move that was expected to generate 27.5 billion kroner of extra income before 2042.

Those extra billions have been allocated to upgrading Denmark’s rail infrastructure and reducing travel times between the country's major cities.

But according to Jyllands-Posten newspaper, the consultancy firm Wood Mackenzie has now calculated that the government will earn a maximum of 15.4 billion kroner from the tax rule change.

“Wood Mackenzie's calculations match well with our perception of reality,” Arne Westeng, the managing director of Bayerngas in Denmark, told Jyllands-Posten.

One of the major discrepancies between the government’s and Wood Mackenzie's calculations is that the government included future tax revenue from the Svane gas field, located far off the western shore of Denmark.

The 20 billion cubic metre gas field could satisfy Denmark’s gas consumption for five or six years, but currently no company owns a licence to extract the gas after Dong and Bayerngas chose to hand back their 35 and 30 percent respective shares in the field to the government in January.

“There is a considerable potential in Svane but no technology currently exists that will allow us to construct a well that can retrieve gas under the extreme temperatures and pressure found at Svane,” Westeng said.

Westeng has been a vocal critic of the government’s decision to harmonise the tax rules for North Sea oil and gas. In March he said the new rules – which affected only a small number of oil and gas companies – made Denmark an unattractive country to invest in and, as a result, the company was not planning to apply for any future licences in the Danish North Sea.

The government’s predicted oil and gas revenue also rests on an anticipation that oil prices will rise steadily over the coming years, something Westeng argues there is little basis for.

“The calculations in the government’s proposal predict oil to rise from $112 a barrel [today] to $132 a barrel in 2017 and continue to rise thereafter,” Westeng said. “I know of no oil company that would assume this calculation.”

Nartin Næsby, the managing director of the lobby group Olie Gas Danmark, also argues that the government’s figures are too optimistic.

“We don’t know where the 27.5 billion kroner is supposed to come from,” Næsby told Jyllands-Posten. “In general, I’d add that tightening tax regulations does not increase oil companies’ desire to invest.”

The Danish energy agency, Energistyrelsen, confirmed that while the Svane field had been returned to the state, revenue from Svane was included because the government expects new technology to make the gas extraction possible.

“Oil and gas is now being commercially retrieved in ways that were previously impossible,” Tue Falbe-Hansen, an Energistyrelsen spokesperson, told Jyllands-Posten. “It’s therefore reasonable to assume that the technology necessary to retrieve it will be possible in a few years time."