The change has come about following a review of the assurance scheme's standards, when it was decided that all Red Tractor vets should be members of PVS, not just those carrying out Real Welfare assessments, as was previously the case.
Other changes in the review focus on the responsible use of antibiotics and a number of the animal medicine standards have been strengthened.
Red Tractor says the PVS membership requirement is in line with another new standard which will require veterinary surgeons to declare they only prescribe antibiotics for use on Red Tractor pig units in accordance with the PVS Prescribing Principles for Antimicrobials.
Red Tractor technical manager Joanna King said: "Ensuring every Red Tractor registered vet is a PVS member will help keep them abreast of the most recent version of the Prescribing Principles, along with other guidelines and publications."
Assessors undertaking Red Tractor farm assessments can verify whether the retained farm vet is a current PVS member through their membership number which is required on the quarterly veterinary report forms.
Membership numbers can be checked against an online PVS membership checker.