Industrial action by postal workers is set to come a step closer when union leaders are expected to endorse the threat of a mail boycott.
The Communication Workers Union (CWU) is raising concerns about the future of the postal service as private firms "cherry pick" work, and wants the postal regulator Ofcom to intervene to protect the service.
Hundreds of CWU reps will meet in Liverpool to discuss jobs, services and performance standards, and will debate a motion which reads: "The CWU calls upon the regulator to immediately act in line with its statutory duty and intervene to protect the universal service."
The motion warns that companies are targeting profitable parts of the delivery network and calls for private firms to meet the same quality of service and performance standards as Royal Mail.
The union is warning of a "race to the bottom" on the pay and conditions of postal workers and calls for minimum industry standards, underpinned by the so-called living wage.
Details of a possible boycott of private companies' mail will be published in time for the CWU's annual conference in April.
Postal workers could refuse to handle third-party mail - which makes up almost half of all letters delivered by Royal Mail - in the next few months, the union has warned.