The Labour party membership renewal team are phoning me about once a week at the moment. I'm having to explain why I won't be renewing every time so they've asked me to email labourmembership@labour.org.uk and fill in the contact form with an explanation. https://action.labour.org.uk/page/s/membership-contact-form

This is what I sent:-

While I broadly support the Labour Party and it's principles, I will not be renewing my membership until the Labour Party formally commits to stopping Brexit and cancelling Article 50.