Duff & Phelps has detailed its case for "consequential losses" in legal documents now lodged with Collyer Bristow, the firm which led the negotiations that saw Whyte buy the club for just £1.
Allegations of professional negligence and a breach of rights and obligations are also understood to have been levied against the firm by administrators, who said yesterday they intend to announce a preferred bidder for the club later this week.
The legal move is the latest attempt by Duff & Phelps to reclaim money owed to Rangers, but Collyer Bristow said the claims would be contested "in the strongest possible terms".
A spokesman for the law firm said: "Collyer Bristow received detailed particulars of the claim on behalf of the administrators Duff & Phelps. A significant proportion of the damages claimed by the administrators [in excess of £25m] relates to claims for 'consequential loss', which we believe to be highly speculative.
"As we have previously stated, it is our intention to contest all claims brought by the administrators in the strongest possible terms, and this remains our position."
The administrators have previously attended the High Court in London to secure access to £3.6m held in Whyte's client account with Collyer Bristow. The firm did not contest this move and the parties were due to return last month to lay claim to the funds, which the administrators claimed formed part of the £24m secured by Whyte through the Ticketus deal on future season ticket sales. A further court hearing to decide who was entitled to that money was suspended after Duff & Phelps announced the "wider claims" against the law firm, which are linked to the way the takeover deal was structured.
QCs have now been appointed on both sides to fight out the claim in the High Court at a later date.
Paul Clark, joint administrator at Duff & Phelps, said: "We can confirm we have instigated legal proceedings against Collyer Bristow, the former lawyers of the club, and The Rangers FC Group Limited in the High Court in London for substantial damages suffered by Rangers Football Club."
Gary Withey, the former partner at Collyer Bristow who led the takeover deal, broke his silence last week over why he left the firm as the crisis at Rangers started to unravel. He told The Herald his career had been "destroyed" by the Ibrox controversy, with him choosing to leave the firm because of the "embarrassment and shame" he felt over the deal.
Mr Withey, who was appointed as club secretary at Ibrox following Whyte's successful takeover, said he regretted the day the tycoon instructed the firm to lead the deal.
The legal action against Collyer Bristow comes as the administrators prepare to announce the preferred bidder to take over the club. While the Blue Knights consortium, headed by major shareholder Paul Murray, has "stepped back" from the process, it has not withdrawn its bid. Singapore businessman Bill Ng and American entrepreneur Bill Miller also remain in the mix.
Both the Blue Knights and Bill Ng have been working with Ticketus as partners on the bids.
Mr Clark said last night: "We would like to inform all Rangers supporters that today discussions have been held between members of the administration team and the two remaining bidders in the sale process. A number of issues have been examined and we have made it clear to all those involved in the bidding it is of paramount interest to the football club a satisfactory deal be concluded without any further delay. It is our intention to announce a preferred bidder this week and we can assure all supporters we are doing everything in our power to make that happen."