The Gers have been out of the SPL since 2012.
Rangers’ plunge to the bottom of the Scottish football league three years ago has reduced interest levels in the Scottish game, with Celtic facing no real threats in their pursuit of domestic honours.
The Gers are flying in the Championship at present and look well on course to make their return to the Premiership next season.
“My view is they need Rangers back in the league to push them on,” said Lambert, on the ‘Alan Brazil Sports Breakfast’ show on talkSPORT this morning (aired at 08:16).
“Celtic are a fantastic football club, with a brilliant set of supporters as everyone knows but I think they need Champions League football and if they’re not going to get that they’ve got to try and progress in the Europa League and that’s what they’re finding difficult at the minute.
“Everybody expects them to win the league (without Rangers) and it’s tough to compete in Europe because of the financial situation in Scotland.”
Rangers’ absence in the SPL has increased the pressure to deliver on the European stage at Celtic but a lack of competitiveness in the league hasn’t helped on the financial front.
The Hoops have therefore struggled to build a team capable of mounting a sustained challenge in Europe and fans have been left feeling underwhelmed despite their domestic success in recent years.
A return to the top flight for Rangers will bring about a much greater general interest in the SPL and the financial benefits will be sizeable, meaning despite the bitter rivalry, Celtic fans should welcome the return of their neighbours.