Nordea is named in The Panama Papers, a huge cross-border journalism collaboration that has been analysing millions of records held by an international law firm based in Panama.
The Swedish bank is listed alongside around 500 other banks or subsidiaries including global household names such as HSBC, UBS and Société Générale, as creating offshore companies through the legal firm, Mossack Fonseca.
The global investigation by the International Consortium of Investigative Journalists (ICIJ) looked into the leaders, criminals and celebrities using secretive offshore companies.
Some 140 politicians and public officials around the world are mentioned in the research. These include 12 current or former world leaders including the president of Ukraine, Pakistan and Iceland's prime ministers and the king of Saudi Arabia.
In total, around 400 Swedes are named in the ICIJ's report.
Reacting to Nordea's role in the scandal, Sweden's Finance Minister Magdalena Andersson told Swedish reporters: “It is a crime — tax evasion — it is totally unacceptable”.
“I mean, the whole of the Swedish [business] model is based on the fact that you accept and pay taxes,” she added.
Sweden's financial supervisory authority, Finansinspektionen, has said that it will launch an investigation into Nordea's overseas activities.
“We did not know anything about this until yesterday,” the agency's head Christer Furustedt told the TT news agency.
Speaking to public television network SVT, the CEO of Nordea's Luxembourg division, where many of the tax deals are understood to have been facilitated, confirmed that the bank had helped customers to create secret 'letter box' companies in tax havens.
“We had a small number before. Now it is a very low number of these kinds of structures,” said Thorben Sander.
However documentation seen by the ICIJ suggests that at least 100 secret offshore companies facilitated by the bank remain active.
“Neither we or our customers think that this feels acceptable, obviously it is very regrettable,” Nordea's press officer Magnus Nelin was quoted as saying by the TT news agency.