London Welsh have confirmed they will appeal against the Rugby Football Union's decision to block their promotion to the Aviva Premiership.
The Exiles won the Championship title on Wednesday night, beating Cornish Pirates 66-41 over two legs, but the RFU decreed the club had failed to meet the minimum standards to be allowed into the Premiership.
London Welsh chairman Bleddyn Phillips said: "We shall be lodging an appeal in the very near future and in parallel we are pursuing all other available opportunities to make sure we can take our rightful and deserved place in the Aviva Premiership."
London Welsh were informed last Wednesday, just hours before the first leg of the Championship final, that they would not be eligible for promotion if they won the title.
The RFU board had ratified the findings of an independent audit which confirmed London Welsh had failed to meet with the Premiership's minimum standards. The report highlighted primacy of tenure of London Welsh's nominated home ground - the Kassam Stadium in Oxford - as a key issue.
Phillips, a partner in the law firm Clifford Chance, described the RFU's decision as "inequitable, unreasonable and unfair".
London Welsh are frustrated that they have been denied a place in the Premiership when founder members London Irish, Saracens, Wasps and Sale have all used stadia without holding primacy of tenure. The last team to be denied promotion were Rotherham in 2002.
That situation prompted First Division Rugby - the forerunner to the Championship - to lodge a complaint with the Office Of Fair Trading against the RFU and Premiership Rugby. The OFT ruled that clubs no longer had to be the main tenants at their home stadium but they must be able to stage matches at a venue on dates specified in advance by the Premiership.
London Welsh insist they have a legally-binding agreement with the owners of the 12,500-capacity Kassam Stadium that would come into force if they are promoted. The Exiles argue they can meet the fixture scheduling demands of the Premiership.
An RFU spokesman said they would not make any comment until an appeal had been officially lodged.