In a statement released late on Thursday, the Malaysian Consultative Council of Buddhism, Christianity, Hinduism, Sikhism and Taoism said the government had no legal right to ban the use of a word that predated the Koran and Islam.
The council "views any attempt to proscribe the use of the term 'Allah' in any way to any religion as untenable from the standpoint of language, theology or history," it said in its statement. "No religion can claim exclusive possession or use of this term."
Malaysia's constitution declares it a secular state but with Islam as its official religion. About 60% of Malaysia's 25 million people are Muslims.
Last month, the government lifted the ban on the use of "Allah" in the Herald, the country's main Roman Catholic newsletter, after the publication's editors took the matter to court for the right to use the word.
The Herald had argued that the Arabic word is a common reference for God that predates Islam and has been used for centuries as a translation in Malay.
However, their victory was short-lived as the government revoked its decision two weeks later after fierce outbursts from Islamic hardliners.
A spokesperson from the country's National Evangelical Christian Fellowship said on Friday that the ban was "purely a political move".
"The term has been used for years by Christians and is even used in the Indonesian Bible," he said on the condition of anonymity because of the sensitivity of the issue.
"We believe this is nothing more than a political gimmick and it won't stand for long," he said. "We should be seeing the light at the end of the tunnel soon."
The spokesperson declined to elaborate on what the group would undertake if the ban remained.
Malaysia's minorities have often complained that their constitutional right to practice their religions freely has come under threat from the Muslim-dominated government.