When all is said and done, both the parliamentary Conservative Party and Labour Party decided that implementing a narrow Leave win in an advisory referendum took precedence over protecting and safeguarding the Union. They took the decision to trigger Article 50 despite the fact that Scotland had voted clearly to Remain as had Northern Ireland. They did so irrespective of the fact there was not even an outline solution to the NI issue nor any view on the multiple types of Brexit possible. You could expect this from the Tories being under pressure from their loony right wing but Labour had no excuse. Once that hasty flawed decision was made, it was inevitable that any wrongdoing around the referendum (and there was an unprecidented amount) would be quickly kicked into the long grass and strangled.
Chickens have come home to roost and it is clear now that the Tories are driving hard for either a no deal or hard Brexit that ensures there is minimum alignment with the EU. Labour have slowly, glacially, moved their position from being a pro brexit party to one that wants the best of both worlds. History will not judge this process kindly and in the future it will be seen for what it is. A total abdication of parliamentary responsibility to do what should of been its primary responsibility, protecting the fabric of the Union.