Labour's election manifesto is available here, and it makes very strange reading. It is all about what it has achieved in the EU and what its MEPs will be working for, while at the same time Corbyn says during the launch of the manifesto in a Q&A session:

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Q: You say leave or remain are unhelpful labels. But many in your party want it to be a remain party? Is it definitely a leave party? Or could it be a remain party?
Corbyn says he fought the referendum on a remain and reform programme. But leave won.
He summarises the sort of Brexit he wants. And he says the Labour manifesto includes the option of a public vote.
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Getting the Brexit he wants is still Brexit (even if some call it BRINO), so much of what is written in the manifesto saying what the MEPs would be doing evaporates.

The manifesto is written on the assumption we are leaving. For example, "Labour will campaign to secure the continued access to vital databases, which have helped take criminals off our streets and in the fight against terrorism" only makes sense if you have left: if we remained we would have that access.

I for one could not vote for Labour in the upcoming EU elections on the basis of this manifesto. However, I very much doubt if confirmed Leavers will either. I anticipate much of Labour's anticipated vote will move to other parties.