* Regional union branches recommend 6 pct wage rise demand
* Recommend right to reduce weekly hours to 28 from 35
* German labour minister welcomes call for flexible hours
* Employers reject IG Metall branches' recommendations
* National wage demand due Oct. 26 (Adds IG Metall Baden-Wuerttemberg, German labour minister, industry association)
FRANKFURT, Sept 14 (Reuters) - German trade union IG Metall fired its opening shot in the 2018 wage round on Thursday, with regional branches from industry-rich states recommending a 6 percent wage rise demand and a right to shorter working hours.
That compares with a national demand of 5 percent in the last round in early 2016, which resulted in a settlement of a 2.8 percent increase on July, 1 2016 and a further 2.0 percent on April, 1 2017.
Working time is set to form a central plank of this year's wage round. IG Metall is campaigning for a right to reduce weekly hours to 28 from 35 -- with a right to return to full-time work after two years -- for shift workers and those caring for children or other relatives.
Germany's biggest trade union, whose workers are mainly in the car and manufacturing industries, wants employers to contribute to making up the shortfall in pay for the cut in hours.
"Inflation and productivity are rising, capacity utilisation by the companies is at the highest level, and order backlog is excellent," the regional branch of IG Metall in the populous western state of North Rhine-Westphalia, home to industrial companies like Thyssenkrupp, said.
The branch in Baden-Wuerttemberg, where carmakers and suppliers like Daimler and Robert Bosch as well as many of their suppliers are based, said workers needed more opportunities to balance their work and private life.
German Labour Minister Andrea Nahles said she welcomed IG Metall addressing the issue of working hours, given that in many families both parents work and modern technology made it possible to work at any time and in any place.
"If Germany's economy wants to effectively combat the shortage of skilled workers and achieve high rate of participation in the labour market by both men and women, then it needs to give workers the opportunity to adapt their working hours to their life situation," she said in a statement.
Industry groups in North Rhine-Westphalia, Baden-Wuerttemberg and Bavaria said the union's wage demand recommendation was excessive and rejected the idea that employers should pay staff who cut their hours for work they have not done.
"And the union makes no constructive suggestions how companies can compensate for the lost work without incurring higher costs," Stefan Wolf, head of the metals industry association in Baden-Wuerttemberg, said in a statement.
Regional IG Metall recommendations will feed into a national wage demand that will be announced on Oct. 26. Negotiations will then begin in November.
IG Metall's wage settlement will affect as many as 3.9 million workers, including members at plants not directly covered by the pact, and will have a strong influence on other agreements among workers throughout Germany. (Reporting by Georgina Prodhan and Maria Sheahan; Editing by Keith Weir)