New three-day strike at Swindon's Great Western Hospital
Cleaners at Swindon's Great Western Hospital have started three days of strike action in a dispute with employers over bullying allegations.
It is the latest phase of action against Carillion by GMB union members who have already staged three days of strikes.
GMB's Andy Newman said good industrial relations must be restored within the hospital to "put the dispute to bed".
Carillion said its "lines of communication remain open".
It also said managers would be having "further talks with GMB".
The union submitted a formal complaint by 109 members of staff over allegations of bullying and harassment in December.
Carillion said: "We take matters of bullying and harassment extremely seriously and the collective grievance is being fully investigated."
So far, one hospital manager has resigned over the issue.
Porters, cleaners and domestic staff at the hospital staged 24-hour walkouts on 14 February, 21 February and 23 February.
The RMT union has also pledged support for the GMB after it discovered its members' pension fund was a major shareholder in Carillion's parent company Semperian.