Despite what some people claim, Labour's position is very clear, as Steve says. But in fact you can go further. Labour is trying to get a deal *precisely because* it is respecting the referendum result. If they did not, there would be no need to seek a deal. And any deal they negotiate will be to leave and therefore 100% compatible with the 2016 result, which did not insist on any specific kind of leave, whatever Brexiteers would have you believe. Then they will put it to a confirmatory vote *precisely because* the 2016 did not say how we should leave so it is desirable to ask the question "Did we get this right?"

Also, we can anticipate future criticism that they will deliberately negotiate a bad deal to try to make people vote it down. They are aware the outcome of a second referendum could go either way, so they want all options to be as good as possible because they may have to implement it and live with the consequences.