(Adds trade group comment)
BRASILIA, Oct 4 (Reuters) - Brazil's pension oversight body Previc ordered a 180-day intervention in Postalis Instituto de Previdência Complementar, the pension fund for post office workers, for breaking rules on reserve requirements and investments, the regulator said on its website on Wednesday.
Postalis, Brazil's largest fund by number of participants, has amassed billions of reais in losses over the past decade due to risky bets and has run a deficit every year since 2011.
Previc, which will take over management of Postalis for 180 days, gave no further details. A spokesman for Postalis said the intervention "took us by surprise" and had no immediate comment.
The head of the pensions industry trade group ABRAPP said the situation with Postalis was an "exception" and no threat to Brazil's pension fund system that is solidly capitalized.
Postalis oversees 10.2 billion reais ($3.25 billion) in savings for 155,400 contributing members.
Last year, Reuters reported that Postalis was trying to offload 2.2 billion reais worth of bad loans after a planned sale collapsed amid management changes and feeble demand.
Postalis extended loans to companies for years, a type of transaction that was increasingly used by state-controlled pension funds during the leftist Workers Partys 13 years in power. Some borrowers issued bank credit notes - known in Brazil as CCBs - that Postalis fully subscribed.
The pension fund's accounts turned red with the deterioration in corporate creditworthiness and capital markets activity in Latin Americas largest economy as it slowed down and slid into recession. ($1 = 3.1366 reais) (Reporting by Anthony Boadle; Editing by Susan Thomas and Andrea Ricci)