I posted the email I had sent to Labour's Brexit spokesperson, Sir Keir Starmer, who happens to be my MP. I have now received a reply from him:
I’m very sorry for the slow reply - my apologies
I was quick to criticise Barry G’s comments, which he has retracted
I agree with you about N Ireland and the six tests
To reiterate: if the PM’s final A50 deal fails the six tests, Labour will vote against
The promise to oppose the deal is very significant. From what we have seen so far, it seems likely that any deal might fail all six tests, but two in particular would seem impossible to pass:
1 That the deal should deliver 'the “exact same benefits” as we currently have as members of the single market and customs union'
2. That it must 'deliver for all regions and nations of the UK'
I felt I needed to clarify Sir Keir's promise a little, so I have sent him this reply:
Dear Sir Keir,
Thank you for this. Just to be clear. I take it to mean that if the final deal fails ANY of the six tests, then Labour will vote against it?