(Reuters) -Royal Mail could cut as many as 5,000 to 6,000 jobs by the end of August next year, parent company International Distributions Services said on Friday, as the British company remains locked in a bitter dispute with its largest labour union.

The Communication and Workers Union (CWU), representing 115,000 Royal Mail postal workers, have held strikes in September and early October, and have threatened more strikes this month and next.

Royal Mail would post an adjusted operating loss of around 350 million pounds this year, after taking into account the hit from the strikes that have taken place or are scheduled, International Distributions Services forecast.

“We will be starting the process of consulting on rightsizing the business in response to the impact of industrial action, delays in delivering agreed productivity improvements and lower parcel volumes,” it said in a statement.

The company said there could be more job losses at Royal Mail, its UK business, if strikes went ahead during the holiday period.

GLS, its international distribution network, has been performing in line with expectations, the company said.

The CWU did not immediately respond to a Reuters’ request for comment.

Royal Mail, the former British postal monopoly recently changed the name of its holding company to International Distributions Services from Royal Mail Plc.

(Reporting by Yadarisa Shabong in Bengaluru; Editing by Savio D’Souza)