Ferrari has clashed with its unions over plans to idle production and cut its 3,000-strong workforce by 9% due to falling orders for engines from sister brand Maserati.

Workers walked out for four hours when Ferrari announced it wanted to cut 120 office posts and 150 factory jobs in exchange for the last payment of a 2009 bonus due last month, according to the CGIL union.

The supercar maker wants to idle a factory in Maranello, Italy, by laying off about 600 workers for a  week starting 17 May, the union added. It also said Ferrari was slashing 2010 production targets to 11,000 vehicles from 20,000.

However, a Ferrari spokesman said the company had no target to make 20,000 cars this year and would maintain production at about 6,000 vehicles, similar to last year’s output. The company intends to outsource some jobs to local companies and offer some employees early retirement.

Ferrari made 4,500 engines for Maserati last year, down from almost 9,000 in 2008.

The company said in a statement it was focusing its resources on activities such as “product development, technological innovation and reaching new customers” and has decided to outsource “non-core” operations. This will allow the carmaker to maintain about 100 contract workers.

Fiat CEO Sergio Marchionne unveiled a new five year plan for Ferrari and Maserati last month along with new targets for the entire group and called for the two luxury brands to almost double revenue to about EUR4bn (US$5bn) by 2014 by adding products and widening model ranges.