My friend (yup, it is really someone else

The company is currently preparing some cuts and it is possible that there will not be work for all the 10 people working there full time, plus a few part-timers.
My friend was advised by someone (not a lawyer nor HR specialist) that after 6 months working full time they can not reduce it beyond 30 hours week (about 130/h month). Is this true?
*By full time I mean that he has been given between 160 and 170 hours of work every month, sometimes more. There's no monthly pay, he's paid by the hour.