The Rangers board issued a statement on the club website on Sunday stating that they had no intention of selling Ibrox, following demands from the Union of Fans for a legally binding promise.
But the statement made no mention of the club's training ground.
The supporters' group said: "The Union of Fans were approached approximately two weeks ago, on behalf of the PLC board, to once again try to reach agreement on a binding legal guarantee over the club's assets. These discussions continued and various drafts were passed back and forth.
"We were seeking written guarantees over both Ibrox and Murray Park. The board removed all reference to Murray Park. This was not an oversight - they are explicitly refusing to include Murray Park in any undertaking.
"We believe this is because the board are actively looking to sell this vital club asset due to their failure to so far secure enough funds to see the club through the current season."
The supporters' group had tried to force the board to offer security over the stadium and training ground in return for their season ticket money, but about half of the 34,000 fans renewed directly through the club, while the Rangers board announced plans to raise much-needed money through a share issue later this year.
The statement added: "Currently the club has four main assets. Two of those, Edmiston House and the Albion car park, have already been used as security for crisis loans due to financial mismanagement.
"The board continues to refuse to give any legally binding safeguard over Ibrox and we believe they are actively looking at a sale and leaseback of Murray Park - a vital asset if we are ever to properly develop our own talent. They have shown no commitment to protecting the club's assets."
The club statement had read: "The board is happy to reaffirm its position, which has never been a matter of debate, by confirming once again that it will not enter into any form of sale, securitisation or leaseback of Ibrox Stadium.
''This has been and still remains the board's clear and consistent position on this subject as it continues to protect and enhance the assets of the club."