Chairman King has repeatedly said he will bankroll a spending spree on the squad to the tune of £30 million in order to make Rangers competitive immediately on their return to the Premiership.
Stein trusts the South African-based multi-millionaire will be true to his word and provide Warburton with the necessary funds to find a new spine for the team.
The 68-year-old, who scored the first goal in the 1972 Cup Winners’ Cup final, believes that four top-quality signings will enhance an already talented group that he enjoys watching in his role as matchday host for the hospitality department
He said: “Dave King has promised Mark Warburton there will be money to spend and you can’t go back on that, so I think he’ll need to put his money where his mouth is.
“They certainly need four or five to beef up the numbers because they might not keep everyone they have now.
“If they can only name five subs for a semi-final then something’s not right. I don’t know whether there were kids from the academy who could have been on the bench.
“But I was speaking to Jim Stewart about it and he said there were no other options.
“People are saying they need six or seven new signings to be as good as Celtic but I’m not sure that’s the case. I don’t know anything about the lads who are coming from Accrington Stanley – although I saw Josh Windass’s dad play for Aberdeen – but I don’t know if they can attract better players than that.
“Basically, it all comes down to money. If you look at the Championship in England there are guys earning £20-30,000 per week.
“I don’t think anyone up here can compete with that, including Celtic. So the only way they’re going to get a player from the Premier League is on loan.
“You wouldn’t get a proper first-team player from down there but Warburton needs to build up his squad.”
Stein feels bringing the right players in will make Rangers definite challengers as Celtic are in a state of flux as they search for a new manager which will inevitably lead to major squad changes.
The former Scotland striker believes Celtic’s recent track record on recruitment has been woeful. He said: “I feel sorry for [Ronny] Deila because he’s not picking the players, it’s [Peter] Lawwell and the chief scout.
“They nominate the players and he’s got to agree. I can’t understand that. He should be saying yes or no.
“[Nadir] Ciftci? A million quid? Honestly – I think he’s hopeless. He’s not even still here. The boy [Scott] Allan as well. [Gary] Mackay-Steven’s weak, [Stuart] Armstrong – the three players from Dundee United aren’t going to strengthen the team
“The other thing about Celtic is they have qualifying games at the start of July and whoever comes in might come in and get rid of four or five.
“That’s not going to be good for Celtic. I wouldn’t be taking the job if I wasn’t buying the players.”