I’m one of the signatories of this letter, which calls on Labour to make a confirmatory public vote its bottom line in negotiations with Theresa May.
May has been clear that the legally binding part of the Brexit deal, the withdrawal agreement, cannot be renegotiated. This means that the only concessions Labour could obtain will be non-binding assurances about the future relationship. Any future Tory prime minister could simply rip up these “guarantees” after Theresa May leaves office, and it is the stated aim of the vast majority of Tory MPs to do precisely this.
The only way to guarantee jobs, rights and protections – and Labour’s reputation with its membership and the electorate – is to support a confirmatory public vote on any option which is agreed by parliament.