Ciaran Martin, who was the constitution director in the Cabinet Office between 2011 and 2014 and formed part of the Whitehall team which negotiated the terms of the 2014 referendum, said the future relationship of Scotland and the rest of the UK in the event of a second No vote should be agreed prior to any vote.
Speaking to The Scotsman’s political podcast The Steamie, Mr Martin said such an agreement could include an commitment not to hold another referendum for a minimum time period.
Dismissing the claims the use of ‘once in a generation’ from leading nationalists around the 2014 vote meant demands for a second referendum is invalid, the former civil servant said such an agreement could avoid a similar stalemate to the one currently experienced.
He said: “If there were to be negotiations for a future referendum the UK Government should insist on some form of agreement as to what happens again.
"There is no such thing in the British constitution as a perpetually binding arrangement, but as you know I hold to the view that the once in a generation phrase from the last referendum was just a slogan.
“Electoral campaigns are perfectly entitled to use slogans, it is a direct comparator to the £350m per week to the NHS which I don’t think reasonable people realistically expected to actually be the governing principle of the subsequent period.
"You could insist on an agreement, written down, passed into law – can always be changed – of a minimum period before the issue would come back and possibly, although I favour largely a rerun of the 2014 model, you could at least debate issues of franchise and that sort of thing.”
Mr Martin added that the type of constitutional arrangement planned for Scotland in the event of a No vote should be clearly placed in front of voters prior to another referendum.
Arguing that a “wider adaptation of the UK constitutional model” as unlikely, the mandarin-turned-academic said federalism would constitute a “gigantic revolutionary change” and that England would be unlikely to back such a move.
He said: “There’s not much more left to devolve and federalism is so misunderstood.
“It is a gigantic revolutionary change in the British constitution that I just can’t see England voting for after what it has been through with Brexit, it means the end of parliamentary sovereignty.
"That combined with the wing of modern conservatism that really thinks devolution was a horrendous mistake, really thinks that this promotion of sub-national identities within a multi-national state is a huge mistake and it should all be about Britain.
"Which of those are No voters voting for? Are they voting for the messy, largely devolved, largely autonomous in domestic policy Scotland that we’ve seen through the pandemic?
"Or are you voting for, frankly, a very centralised British state based on anglo-centric British nationalism?
"That can wax and wane with changing political fortunes in UK electoral politics but at the same time I think that is an important question.”