Once again. There wasn't any existing EU constitution for Labour to to have a referendum about. The one referred to had already been vetoed by two other countries.

There was never any kind of promise to have a referendum about membership of the EU in that manifesto.

Unlike the firm and unambiguous promise I mentioned in Tory referendum of 2017: We will maintain all other pensioner benefits including free bus passes, eye tests, prescriptions and TV licences, for the duration of this parliament.