The draft rule said organisations appealing to the tribunal against a Charity Commission decision could recover legal costs if it were shown that the decision had been "irrational".
Law firm Bates Wells & Braithwaite pointed out in its response to a consultation on the rule, which ended last week, that the Charities Act uses the word "unreasonable".
A spokeswoman for the Ministry of Justice said: "Officials are aware that 'irrational' is the wrong word and needs to be changed."
The draft rule that appeals against tribunal decisions must be lodged within 28 days was also challenged by BWB, which said it should be three months to make it easier for smaller organisations.
The law firm added that the tribunal should be able to intervene to ensure a fair balance of resources between parties to a case, and that those who might be affected should be notified so they could participate in proceedings.
A spokesman for the Office of the Third Sector, which is also dealing with the consultation, said that the responses would be considered.