Professor Jim Gallagher has been recruited to the cross-party Better Together campaign as an adviser on policy and strategy issues.
He said that his role would be to “help the parties in the Better Together campaign to put their case across”.
He added he would be “helping the campaign develop the arguments that explain the positive case for remaining in the United Kingdom, and how a strong Scottish Parliament fits into that”.
Prof Gallagher previously served as Secretary to the Calman Commission, which was set up in 2007 to review the devolution settlement.
He told BBC Radio Scotland: “One of the things that we’re inclined to take for granted in Scotland is the constitutional settlement we’ve got, in which we have both a Scottish Parliament and the wider UK back-up as it were. My main job will be to help the campaign to explain the strength of that.”
He rejected claims that the Better Together campaign had been too negative.
“A campaign which is there to persuade people to reject the independence proposition will inevitably have to start by explaining what is wrong with it,” Prof Gallagher told the Good Morning Scotland programme.
“At the back end of last year we had the Scottish Government’s white paper on independence and the campaign were absolutely right to challenge it, to test it, to be critical of it, because to be absolutely frank it wasn’t a particularly strong piece of work.
“There always has been, to be fair to the Better Together campaign, a positive case that it has been making for keeping Scotland in the UK.
“I think my contribution to this is to help unpick and to explain just how it is we have a system in which we have a lot of power devolved to Edinburgh, but can still manage to retain the strength and the back-up of the UK on economics, on defence and on other issues.”
He continued: “There is undoubtedly a story to be told about how the UK hangs together in economic terms and the benefits of that, how the UK works together on defence on security and the interesting story is how we can manage that and still have an immensely wide devolution to Edinburgh of all the powers of domestic policy.
“All of the parties in the Better Together campaign are looking at the devolution settlement at the moment, none of them has come to a firm conclusion, though the Liberal Democrats have produced some relatively detailed plans.”
While he stressed in the first instance it was up to the individual political parties to develop their own proposals for changes to the devolution settlement, he added: “What we learned from the Calman process, the process that gave us the Scotland Act, is constitutional politics is different from day-to-day politics, it has to be worked on very carefully and ideally it has to be worked on in consensus.
“All of the parties in this campaign are looking at this issue, they’ve got a lot of work to do, I’m very happy to help them in that, but the lesson they learned from the last time they did this very successfully is if they work together they can produce material that works.”