Smith's view was given renewed backing by Aston Villa's Martin O'Neill
Rangers manager Walter Smith believes the Old Firm would be challenging the English Premier League's top four - if given the chance to play there.
The proposal to create a two-tier Premier League could be discussed at the league's annual meeting in June.
"If they were lucky enough to be invited then it would take a number of years to build up," said Smith.
"But Rangers and Celtic would not be fighting relegation, they would be adding to England's top four."
Last week, BBC Scotland learned that Bolton chairman Phil Gartside has proposed allowing the Old Firm clubs to move to England as part of a two-tier Premier League of 18 teams each.
Old Firm would challenge English top four
The idea would have to overcome a number of obstacles if it was to come to fruition and Uefa's director of communications William Gaillard said the matter would be something to be decided between the leagues and associations involved.
"It's hypothetical," said Smith. "But, if they did, the level of finance available to Rangers and Celtic would be far greater than the majority of teams in the Premiership.
"But there is no way Rangers and Celtic would be fighting relegation in the Premier League.
"Rangers and Celtic are bigger than the majority of teams in England, never mind anywhere else.
"If you look at Manchester United, you would say that - yes - there is hardly a team in the world who could compete against them on or off the field."
Aston Villa boss Martin O'Neill has already voiced his backing for a possible switch for the Old Firm.
Rangers aiming for five wins - Miller
And he reiterated his belief on Friday that Celtic and Rangers would go from strength to strength in a bigger league.
"It would be an amazing thought," he told the BBC on Friday. "I thought it would've been brilliant when I was manager of Celtic and I've no reason to change my mind now."
But West Brom manager Tony Mowbray, a former Celtic player, earlier this week questioned whether Scotland's two biggest clubs would make a significant impact if they were invited to the Premier League.
Celtic manager Gordon Strachan was keeping his cards close to his chest about the idea.
"It's not going to happen in the next couple of years," he said. "If I'm here and it gets any closer then I'll give you a view."
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