The Sun reports that highly confidential documents which outlined strategy and the pros and cons of attempting to swap Scotland for England were shared between the two clubs with Hoops supremo Peter Lawwell negotiating with his Ibrox counterpart Martin Bain.

The report claimed the Glasgow rivals - described in the documents as "giant" teams - would have a "massive impact" on the English Premier League and that their departure would benefit Scottish football - because the top flight would become more competitive with Hearts, Hibs, Aberdeen and Dundee United all mentioned as potential title contenders at the time of the talks in 2011.

A section from the dossier claimed: "In a media environment craving additional quantity and quality of games, the introduction of Celtic and Rangers into the Premier League would have a massive impact on the ability to meet that demand."

Peter Lawwell (left) and Martin Bain pictured in March 2011, around the time the two clubs were plotting a Scottish exit

The report said that the large travelling support enjoyed by both teams would result in a "welcome revenue boost for many clubs", adding: "The two teams also benefit from a global following similar to that enjoyed by only a few teams in England such as Manchester United and Liverpool.

"True competition" in Scotland

"Driven by Scottish and (in the case of Celtic in particular) Irish migration, the USA, Canada and Australia provide large, wealthy and committed fan bases.”

Insisting that "increasing true competition is the best way to breathe fresh life" into the Scottish league system, the report claimed: "Teams like Dundee United, Aberdeen, Hearts, Hibs and others would have the chance of competing for a title and of being crowned Champions — and a place in the UEFA Champions League.

“Cities outside Glasgow would, for the first time in generations in some cases, have the chance of tasting success. The long-term financial model would be more sustainable.”

The report made claims that Scottish youngsters would be "inspired" by seeing top footballers playing in Glasgow on a weekly basis while both clubs were keen to continue competing in the Scottish Cup despite eyeing a move to the English pyramid.

Bain and Lawwell were due to sit down with Ralph Topping and Neil Doncaster - at the time, the chairman and chief executive of the Scottish Premier League - in November 2011, but Rangers' financial struggles meant the meeting was never held.

Celtic and Rangers 'sent secret emails to each other' as Old Firm rivals plotted England move