One of three companies vying to take over banking software company GBST has taken the matter to the Takeovers Panel, claiming that unacceptable circumstances arise from one of the competing bids.UK company FNZ Group has applied to the Takeovers Panel to have a "process deed" that the GBST board has granted to a rival bidder cancelled.Over the past week, GBST has announced receipt of offers from a local rival, Bravura Solutions, FNZ Group, and Nasdaq-listed SS&C Technologies.The most recent offer, from FNZ, was for A$3.65 a share. However, the GBST board has opted to go with SS&C Technologies, which is offering $3.60 a share. Bravura is out of the picture, with an offer of $3 a share.GBST's chair Allan Brackin said in a statement to the ASX: "Having carefully assessed the merits of both proposals, the board remains of the view that it is in the best interests of GBST and its shareholders to facilitate a binding offer from SS&C."This announcement prompted FNZ to go to the Takeovers Panel. Its application says: "The SS&C process deed was entered into prematurely, contrary to the best interests of GBST shareholders, without facilitating a proper auction process designed to achieve the best price and where providing due diligence access to SS&C will materially reduce the value of GBST to all other bidders."Bidding for GBST has been going on for months. Bravura first made an offer of $2.50 a share on April 12 and has made two revised offers since then.In response, the GBST board engaged with a number of other parties and then launched a confidential tender process, inviting selected parties to submit proposals.FNZ and SS&C made their opening bids on June 28, at $3.15 and $3.25 a share respectively.Following a detailed review of the proposals received, the GBST board formed the view that the SS&C proposal was superior. Its position did not change when FNZ increased its bid to $3.65.