(Adds amount being offered to workers, past redundancy plan)
RIO DE JANEIRO, April 1 (Reuters) - Brazil's embattled state-run oil company Petroleo Brasileiro SA said on Friday it will launch a voluntary layoff program to cut an estimated 12,000 jobs in a bid to save up to 33 billion reais ($9.20 billion) by 2020.
The program will cost 4.4 billion reais and is open to all employees, according to a statement from Petrobras, which has been hard hit by low oil prices, refinery project problems and a massive price-fixing, bribery and political kickback scandal.
The company said the planned redundancies would help adjust the size of its workforce to a smaller investment plan and boost productivity.
Investors have long criticized Petrobras for over hiring and struggling to cut some of the 57,000 people it directly employs when things get tough. Many of its workers enjoy job security that is close to that of civil servants, a legacy of the company's heritage as a full state company.
Under the plan, employees will be offered between around 212,000 reais and 706,000 reais to take redundancy, Deyvid Bacelar, the Petrobras board member representing workers, told Reuters, citing an internal memo.
The move comes on the back of a plan announced in January to cut the number of managers at the firm, and a previous redundancy scheme announced in 2014.
Petrobras is set to slash its five-year investment plan by about 20 percent to about $80 billion in the 2016-2020 period, sources said a month ago.
Petrobras reported a fourth-quarter loss of 36.9 billion reais ($10.2 billion), its biggest quarterly loss ever, after booking large writedowns for oil fields and other assets as oil prices slumped and refinery projects faltered.
A year earlier, writedowns also caused hefty losses, although they were largely related to the corruption scandal that has roiled the company and fueled calls for the impeachment of Brazilian President Dilma Rousseff.
$1 = 3.5883 Brazilian reais Reporting by Marta Nogueira and Silvio Cascione in Brasilia; Editing by Chizu Nomiyama, Phil Berlowitz and Paul Simao