By Charles Duxbury 

STOCKHOLM--Sweden's former finance minister, Anders Borg, continued his smooth transition to the private sector Tuesday, signing on with Citi as an adviser.

The job is Mr. Borg's fourth assignment since quitting politics in the fall after his center-right party lost a closely fought general election.

He already heads a project on improving the way the financial sector works for the World Economic Forum, an institution promoting interaction between the public and private sector. He has also joined the boards of Swedish investment company Investment AB Kinnevik and the Kinnevik-controlled telecommunications company Millicom.

Alongside that he is compiling a report for Finland's government on how the country should meet its mounting economic challenges.

Mr. Borg's association with Citi is a coup for the bank, which is seeking to expand in the Nordics, a market dominated by the four big local players Nordea, SEB, Swedbank and Handelsbanken.

Citi has had a presence in the Nordics since the early 1970s and is hoping Mr. Borg's expertise will boost its efforts to increase market share, the head of Citi's Nordic investment banking unit, Eirik Winter, said.

Mr. Borg--Sweden's finance minister between 2006 and 2014--was one of the few European lawmakers whose reputation was enhanced by his response to the economic crisis that gripped the region for much of his time in office.

He won admiration even among his political adversaries with his combination of budget discipline in the good times and measured use of fiscal stimulus during the downturns.

As it began to look likely that Mr. Borg's party, the Moderate Party, might lose power at the 2014 elections, speculation grew that he might step up and take over as party leader from Fredrik Reinfeldt.

However, Mr. Borg repeatedly rejected the idea, telling The Wall Street Journal in a 2011 interview that he saw his time as a lawmaker as a break from a career in the private sector. He worked for ABN Amro, among other institutions, before entering politics.

Write to Charles Duxbury at charles.duxbury@wsj.com

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