The shareholders seeking change in the Rangers boardroom claim that a former employee of the Ibrox club reported concerns to the Serious Fraud Office about payments made during last December's Initial Public Offering of shares.

The group, which is backed by the Glasgow businessman Jim McColl, called for the Rangers financial director Brian Stockbridge to resign, and described his position as untenable.

The group - it has nominated four new directors - also claimed to have received a statement from the former employee about the payments.

In a previous interview, McColl raised questions about the costs ­associated with the IPO, which gene­rated £22m, saying they were significantly higher than the costs of IPOs he had been involved in.

Stockbridge has also been criticised by supporters for filming the former chairman, Malcolm Murray, during a night out, and for accepting a £200,000 bonus for Rangers winning last season's Third Division title.

"We believe that the position of Brian Stockbridge is completely untenable and he should resign or be voted off the board at the agm," said the group in a statement. "He has presided over significant outflows of cash from the club since the IPO. In addition, his personal conduct has fallen a long way short of the standards expected at Rangers Football Club.

"We have been provided with a statement from an ex-employee of the club questioning various payments made to certain shareholders around the time of the IPO. The ex-employee has reported the matter to the Serious Fraud Office."

The SFO does not respond to queries due to operational reasons, and a spokeswoman said yesterday that they "decline to comment" on this matter. Rangers issued their own statement, claiming that they have not been contacted by the SFO, and are "unaware" of any investigation. "We can only assume that confidential information that an ex-employee leaked to the requisitioners was in relation to the payments to certain shareholders that was looked at by two sets of lawyers and the nomad [nominated advisor] at the time and then subject to an ­additional specific review," said the club in a statement.

The McColl group has nominated Paul Murray, Malcolm Murray, Alex Wilson and Scott Murdoch as new directors, and shareholders will decide the make-up of the board at next month's annual meeting. The four nominees have pledged to work for free until the club returns to the top flight, with finances tight and fresh funding likely to be required by the end of the season.

Despite Laxey partners having consolidated the shareholdings of the pro-board supporters last week, and becoming the largest single shareholder in Rangers International Football Club before declaring their support for the current directors, the McColl group continues to have the backing of institutional shareholders and they have pledged to continue their campaign for change. They also challenged the three recently-appointed Rangers directors, David Somers, Norman Crighton and Graham Wallace, the chief executive, to display their independence from the previous regime.

"In July we embarked upon a campaign to remove certain directors from the board and to prevent Charles Green from returning to the club, which he was attempting to do at that time," the group said in yesterday's statement.

"We were supported by other like-minded individuals, including major institutional shareholders and the fans, and, in particular, we were all concerned about the significant outflows of cash since the IPO and the obvious dysfunctionality of the board. Since the IPO, the club has had three chairman, three chief executives and three nomads. This is highly unusual for a public company and may even be unprecedented.

"In the last four months, we have seen Green banished from the club, followed by three of his fellow directors. Of the six directors who were on the board when we started, only two remain. In the past three weeks there have been three new appointments to the board. On paper these look like credible individuals who appear to be independent of the Green or Whyte regimes. They will have the opportunity over the coming weeks to prove this and to gain the trust of the fans.

"On October 14, we won our case at the Court of Session to have four individuals, Paul Murray, Malcolm Murray, Scott Murdoch and Alex Wilson, nominated for election to the board at the agm. As well as being supporters, all four have had highly-successful business careers. All four are prepared to waive any director fees until the club is back in the [Premiership]. We will continue our campaign and we would encourage all fans and shareholders to support the changes we have been fighting for."

In their statement, the Rangers board denied that there has been a lack of financial transparency, and also that the new directors will help to "deliver the highest standards of corporate governance", and that Stockbridge had reduced costs.

"The outflows of cash include a large amount of exceptional running and salary costs that were inherited from the previous board, costs that were initiated by Malcolm Murray when he was chairman," the statement continued.

"Despite this, Brian Stockbridge has addressed planned expenditure from facilities, made substantial savings on security by bringing it in-house and making it a revenue generating centre, and saved substantial amounts from the catering contract. It will have escaped nobody's attention that Mr McColl and his colleagues are appearing at a fans forum in Glasgow [tonight] and [their] statement appears to be a crude attempt to garner support."