Jim McColl has revealed he is not looking to lead a Rangers takeover as Charles Green challenged him to put his own money behind a boardroom coup.

The wealthy Scottish businessman issued a statement publicly confirming he was putting his weight behind calls for boardroom change in his capacity as a Rangers shareholder.

Engineering tycoon McColl, whose personal wealth was estimated at £1billion in last year's Sunday Times Rich List, backed outgoing chairman Walter Smith's calls for fans to get behind formal moves to install Paul Murray and Frank Blin on to the board.

But at around the same time, former chief executive Green arrived back in Scotland and issued his own demand, effectively urging McColl to put up or shut up.

In his statement, McColl, the Clyde Blowers chairman and chief executive said: "Let me make it very clear, I am not seeking to join the board or to increase my shareholding in the club.

"I am a small shareholder like many of the club's fans and have no intention of increasing my position in the short to medium term.

"I am 100 per cent focused on my own businesses and the strategy which I have agreed with the investors in my funds. I am duty bound to honour that agreement.

"This is not because I don't believe investing in Rangers would be a good investment, it is because of the commitment I have made to my own businesses and to my partners.

"On the contrary, I believe that with a strong reconstructed, effective and highly competent board to restore financial transparency, stability and success to the club, it is a very attractive investment opportunity.

"This requisition for change is not about any one person or group of people trying to gain a controlling position, this is a demand for change by some very concerned investors, fans and other stakeholders.

"Things have to change to allow the club to move forward with ambition and confidence.

"The board needs to be constructed to reflect balance, independence and experience to operate in the best long-term interests of the club, fans and shareholders rather than the interests of a small clique."

Read Jim McColl's statement in full

Green hit back, saying: "What I say to Jim McColl, the world's richest Scotsman, is put £14m in a bank account by Friday of this week and me and my consortium will deliver to you 20m shares.

"That is about 28% of this club and then I will know that you are serious about it. You have then invested some cash in the club you want to run.

"However, you are not going to do it without putting some money on the table and, up to today, and after 18 months, none of you have done it.

"We have a group of people - Paul Murray, the Blue Knights - who were going to buy (the club) from Duff and Phelps and failed.

"Paul Murray was on the board of Rangers when Craig Whyte bought it for £1. Well, if he had given David Murray £2, he would have bought it but maybe Paul Murray didn't have £2 at the time.

"We have a situation from time to time where these people surface.

"After I'd bought the club, the Blue Knights again, through Douglas Park and various people, said: 'We'll buy it off you.'

"Walter [Smith], regrettably for him, agreed to allow his name to be put at the front and he was let down again because they didn't turn up with any money.

"These people consistently mess with this club and mess with the minds of Rangers fans and don't deliver."

Asked why he believes Smith had to step down from the role, Green said: "I think Walter had issues three or four times.

"He actually came to see me in the first week in April and said to me: 'Look Charles, I'm going to step down.'

"He said: 'I don't enjoy being on the board because of the way Charles Green does things - bull at a gate' and we laughed about it.

"At that time, I was having difficulties, as all the fans and the press know, with Alistair [McCoist] and, of course, Walter is very loyal to him and that's quite right.

"But also, from Walter's point of view, which he said himself recently, he's not a businessman, he doesn't understand plc and he made the point that he would be stepping down.

"I think recent events have accelerated that decision and it's sad for the club that Walter has stepped down but the club has to move forward and not look backwards."

Green himself stepped down as CEO in April, amid claims of close links with discredited former owner Craig Whyte at the time of the Green consortium's acquisition of Rangers' business and assets last summer.

Green added: "The club is an absolute mess. I left the club in April to allow it to move forward, to get on, for me not to be involved because of the Craig Whyte issues.

"What I wanted to do was to see Rangers prosper and I think if you read Walter's statement yesterday, he made the point that the board is completely disfunctional and couldn't agree on anything.

"That never happened in my time because I ran the company and I made the decisions and there are no decisions being made on that board recently because of the arguments between it.

"Of course, Malcolm Murray stepping down - all of these things are a tragedy for the club."

McColl was involved in an unsuccessful bid to buy Rangers from Green's consortium immediately after it bought the liquidation-bound club's assets and business for £5.5million in June last year.

But his involvement now is as a member of a group of disgruntled shareholders, albeit an influential one, who last week called for former PricewaterhouseCoopers Scotland executive chairman Blin and former oldco Rangers director Murray to join the board.

The group wants Craig Mather to be removed along with Bryan Smart and Brian Stockbridge, both of whom are associates of Charles Green, and have demanded an extraordinary general meeting, a request the board is considering.

McColl said: "I would support Walter's call and urge the board to do the right thing and accept the changes proposed in the requisition recently received from a group of concerned investors.

"Acceptance will avoid the unnecessary expense, disruption and delay of a general meeting.

"This is an important step towards building a strong, effective, highly competent board to restore financial transparency, stability and success to the club."

Smith's decision to quit came three days after the club announced the return of Green as a consultant. Green is back less than four months after he resigned as chief executive amid an investigation into his links with former Rangers owner Craig Whyte. And McColl hopes the former Rangers boss can be restored to the board at some stage.

McColl said: "Walter as chairman should have been given the position he has rightly earned to be an ambassador for the club, to offer wise counsel in the many facets of the club's operations, ranging from representing the club; helping set the club's tone and standards; working with the communities we serve; liaising with the fan base and helping the club rebuild its reputation with the football regulators."

Smith argued Mather should be allowed to continue as chief executive but McColl believes he should step down from the board and "remain as a candidate for the role alongside external candidates as part of a formal selection process".

McColl added: "The board should undertake a proper search to identify the best candidate for the job."