Hospice Aid UK, which gives grants to hospices across the UK, objected after the hospice support charity Help the Hospices rebranded itself Hospice UK in 2014, claiming the name was too similar to its own.
Hospice Aid UK believes the name change has caused confusion and has resulted in donations being sent to the wrong charity, Third Sector understands.
But the Charity Commission declined to intervene, despite warning in its guidance on naming a charity that it might ask a newly christened charity to change its name if its similarity to an existing charity was likely to cause confusion.
The regulator, which in August 2014 opened a still unfinished statutory inquiry into Hospice Aid UK’s governance and fundraising arrangements and whether it was being used for private gain, declined to comment on its decision not to get involved in the dispute because it was the subject of ongoing litigation.
A Charity Commission spokesman said: "We are aware of this case and are defending it."
The tribunal has not yet accepted the appeal because it is deciding whether or not it has jurisdiction to require the commission to issue a direction and has asked the commission for advice.
The commission spokesman said: "We wrote to the tribunal yesterday to explain our view that the tribunal does not have jurisdiction in this case, because its jurisdiction is limited to the decisions, directions and orders listed in Schedule 6 of the Charities Act 2011, which does not include this decision.
"While the tribunal has jurisdiction to hear an appeal against a direction actually made by the commission under section 42 of the Charities Act 2011, for example an appeal by a charity required to change its name, the tribunal does not have jurisdiction to hear an appeal against a decision by the commission not to issue a direction."
He said the tribunal was expected to rule on accepting the appeal in the near future.
Hospice Aid UK first registered with the commission in 2002. In the year to 31 March 2015 it had an income of £647,000 and spent £672,000. In the same year, Hospice UK received £6.4m and spent £6.8m, having first entered the charity register as Help the Hospice in 1992.
A spokeswoman for Hospice UK said: "After extensive consultation with our members and other stakeholders, we changed our name to Hospice UK and underwent a rebrand to better reflect the diverse range of hospice care organisations we represent and the services they provide.
"In June 2014 the Charity Commission approved the new name and agreed to register it. No objections were raised by Hospice Aid UK at that time."
No one from Hospice Aid UK was available to comment.