Image caption Vatican officials are concerned about the stance taken by the nuns on several social issues

The Vatican has ordered a crackdown on a group of American nuns that it considers too radical.

It says the group is undermining Roman Catholic teaching on homosexuality and is promoting "feminist themes incompatible with the Catholic faith".

The Leadership Conference of Women Religious is the largest organisation of Catholic nuns in the US.

An archbishop has been appointed to oversee its reform to ensure that it conforms to Catholic prayer and ritual.

The Leadership Conference, which is based in Maryland, represents about 57,000 nuns and offers a wide range of services, from leadership training for women's religious orders to advocacy on social justice issues.

Vatican concerns

But its activities have clearly worried the Roman Catholic hierarchy.

...a prevalence of certain radical feminist themes incompatible with the Catholic faith Vatican report

The Congregation for the Doctrine of the Faith said the nuns' organisation faced a "grave" doctrinal crisis.

It said issues of "crucial importance" to the church, such as abortion and euthanasia, had been ignored.

Vatican officials also castigated the group for making some public statements that "disagree with or challenge positions taken by the bishops", who are the church's "authentic teachers of faith and morals."

The review will include an examination of ties between the Leadership Conference and Network, a Catholic social justice lobby.

Network played a key role in supporting the Obama administration's health care overhaul despite the bishops' objections that the bill would provide government funding for abortion.

The Leadership Conference disagreed with the bishops' analysis of the law and also supported President Barack Obama's plan.

A Vatican report into the group suggested that they "collectively take a position not in agreement with the church's teaching on human sexuality."

In its presentations investigators noted "a prevalence of certain radical feminist themes incompatible with the Catholic faith."

The investigation also found that the group has been "silent on the right to life from conception to natural death, a question that is part of the lively public debate about abortion and euthanasia in the United States".