Image caption Some members of the Leadership Conference held vigils in support of healthcare reform in 2009

The largest US group of Catholic nuns has said a Vatican report finding they had undermined church doctrine was based on "unsubstantiated accusations".

After a three-day meeting, the Leadership Conference of Women Religious said the review was "a flawed process that lacked transparency".

The Vatican investigation said the group had "serious doctrinal problems" and ordered a leadership overhaul.

The Leadership Conference has diverged from the Holy See on a range of issues.

The Vatican report concluded in April that the Leadership Conference had taken positions on issues ranging from homosexuality to the all-male priesthood that undermined Catholic teaching.

It proposed replacing the leadership of the group with three bishops that would have the authority to rewrite the organisation's statutes, meeting agendas and liturgical texts.

"Board members concluded that the assessment was based on unsubstantiated accusations and the result of a flawed process that lacked transparency," a statement from the Leadership Conference said .

"Moreover, the sanctions imposed were disproportionate to the concerns raised and could compromise their ability to fulfil their mission."

The nuns said the Vatican's report has "caused scandal and pain throughout the church community and created greater polarization".

Pat Farrell, president of the Leadership Conference, and executive director Janet Mock also said they would travel to Rome to meet Cardinal William Levada and Seattle Archbishop Peter Sartain - the US clergyman tasked with reforming the Leadership Conference.

The organisation, whose members represent about 80% of nuns in the US, has also said it intends to hold a conference in August to further discuss its response to the Vatican.

Public opinion has rallied behind the nuns as the dispute with the Vatican unfolded. Vigils have been held across the country, including in many major US cities, in support of the nuns.