The man was chairman of Oak Capital at the time that it sold shares to Allra at a significant mark-up from current prices.
At the same time, he was a deputy director in the finance ministry who was on the board of three state-owned companies: Sveaskog, Infranord and Teracom.
Dennis Töllborg, a law professor at Gothenburg University, said the man's role at Oak Capital did not appear to have been cleared by the finance ministry.
"There should be a clear separation between the ministry and that which the ministry is supposed to regulate, especially when matters like pensions and other issues to do with the welfare state are concerned," he told Swedish Radio.
Swedish Radio earlier revealed that Allra did deals on shares worth hundreds of millions of kronor with Oak Capital, despite links between the two companies' managements.
The revelations led the Swedish Pensions Agency this month to expel the fund from the PPM system, under which Swedes are given tax incentives to save privately to top up their pensions.
The agency is also investigating Allra to determine if its arrangements with Oak Capital broke finance regulations.
According to Töllborg, the senior civil servant had been informed that Oak Capital and Allra, then called Svensk Fondservice, were doing deals which Oak Capital's board should have questioned, but had decided to remain on the board.
"When it became apparent that these were questionable deals, possibly even criminal, this person should not only have reacted against them but also have informed the ministry," he said.
Before it was expelled, Allra was the largest dedicated pensions provider in the PPM system, managing 20 billion kronor's worth of pensions investments for 180,000 people.