San Francisco's largest Catholic church has removed a water system after critics claimed it was designed to keep homeless people from sleeping in its doorways.

St Mary's Cathedral, the church led by the Archbishop of San Francisco, had a sprinkler system installed two years ago as part of a drive to remove needles, faeces and other dangerous items from its premises. However local news outlet KCBS, which reported on the system yesterday, said that a cathedral staff member confirmed it was installed "to deter the homeless from sleeping there".

KCBS says it witnessed homeless people being drenched, and said there were no warning signs about the streams of water which fell every 30 to 60 minutes.

The executive director of the Coalition on Homeless, Jennifer Friedenbach,  branded the system "shocking, and very inhumane".

"There's not really another way to describe it. Certainly not formed on the basis of Catholic teachings," Friedenbach said.

A statement from St Mary's admits that the system was "ill-conceived" and "has had the opposite effect from what it was intended to do, and for this we are very sorry".

"The idea was not to remove those persons [who sleep in the doorways of the church] but to encourage them to relocate to other areas of the Cathedral, which are protected and safer," the statement said. The church has been clear that those who regularly slept its doorways were informed in advance about the water system.

"The purpose was to make the Cathedral grounds as well as the homeless people who happen to be on those grounds safer."

St Mary's is heavily involved in programs to help local homeless people, both by offering shelter and food, and helps thousands of vulnerable people each year through the Archdiocese of San Francisco, the statement adds.

"We are sorry that our intentions have been misunderstood."

The church promised yesterday to remove the sprinkler system immediately, after learning that it may violate San Francisco water-use laws.