A self-described 'church' which allows worshippers to smoke cannabis as part of a sacrament has opened its doors in Wisconsin.

Organizers at the Lion of Judah House Rastafari, in Madison, have said 6,000 people signed up to the place of worship in less than a month.

Believers claim the 'religious practice' is protected by the First Amendment which allows the free exercise of religion.

But authorities are skeptical that the establishment is a church at all, Channel 3000 reported.

A flag and sign in the window of the Lion of Judah House Rastafari 'church' in Madison, Wisconsin, which allows worshippers to use cannabis

Cannabis is illegal in Wisconsin except for medical purposes and city bosses are unconvinced by the religious argument.

The mission statement of the 'church' says its aim is to 'freely exercise the religion of Rastafari without burden, lawfully including our only and un-substitutable holy sacrament kaneh-bosm (cannabis)'.

On its Facebook page it describes itself as 'Wisconsin's first and only lawful Rastafari cannabis sanctuary'.

The group says it does not sell cannabis or give it away to the congregation, using it instead as a sacrament.

A membership card says: 'I do exercise my liberty, religion, and conscience, sincerely and legitimately, without a guilty mind, with kaneh-bosm (cannabis) as my sacrament.'

The First Amendment prohibits any law 'respecting an establishment of religion, or prohibiting the free exercise thereof'.

An entrance sign at the purported place of worship where believers claim cannabis use is protected by the First Amendment, which allows the free exercise of religion

The 1993 Religious Freedom Restoration Act has also been used to protect the use of banned substances in religious worship.

But Madison authorities do not believe the organization is sincere about its religious beliefs.

Assistant City Attorney Jennifer Zilavy said: 'They are claiming to be a church. 'I have not seen any documentation or anything that supports they are, in fact, a church.

'Even if they are a church, marijuana is illegal in this state. You can't sell it. It can't just be 24/7 and you can smoke weed and that's our religion.'

A membership card for the Wisconsin 'church' where organizers believe their cannabis use is legal, but authorities are skeptical about whether it is a real church

Police reportedly confiscated 'several jars of marijuana' in a raid last month which was followed by a cease-and-desist letter.

Several U.S. states including California and Nevada have legalized the recreational use of cannabis.

More than 30 states have approved its use for medicinal purposes, as Wisconsin already does.

The drug remains completely banned in certain states including Idaho and South Dakota.

Last year it was legalized for recreational use in Canada.