My Lords, I oppose this amendment on grounds that are rather different from those advanced by my noble friend. I submit that this amendment is wrong in principle, constitutionally improper and unnecessary. Your Lordships might think that given that it was proposed by the noble Lord, Lord Pannick, I am being rather courageous and perhaps foolhardy in suggesting that it is constitutionally improper but I hope to explain to your Lordships why I take that view.
My view is based in particular on subsection (4) of the new clause. That would make possible—indeed it encourages—a never-ending situation in which the Government reach an agreement with the European Union and brings it to Parliament, Parliament rejects it, sends the Government back to the European Union, the Government come back to Parliament and Parliament rejects it again. The only way that process can be ended is by the Government having the power to bring the negotiations to an end. What would happen if the process envisaged by subsection (4) were to take place is the intrusion of Parliament into the negotiating process. That is why I say this amendment is constitutionally improper.