The Church of England has been told to "urgently" update its approach to sexuality, during a discussion at the general synod in York.
On the second day of the synod, member Prof Joyce Hill said there was "a lot of long grass growing" in its plans.
She spoke after the Archbishop of Canterbury, Justin Welby, said the Church would spend three years on a document outlining a new stance.
Current rules ban the marriage of same-sex couples in church.
Services of blessing for civil partnerships are also prohibited, but informal prayers are allowed.
The re-drawn plan follows the synod's rejection of a previous document on sexuality at its meeting in February.
It would be based on what the Church has called "radical inclusion founded in scripture", the archbishop said.
The Church's future policy on sexuality will be decided by two committees: one to consider the ministry the Church offers to same-sex couples; and one to consider its theological teaching.
Prof Hill questioned whether Mr Welby and his fellow bishops were aware of the "great importance" of the matter.
During a question and answer session, she asked: "Are the bishops sufficiently aware of the urgency of this issue?
"The issue is one which is of great importance to the nation; great importance to the relationship between the Church of England and the nation.
"I am very concerned that there's a lot of long grass growing in the programme that is being put before us."
He said: "We believe very firmly that a timescale of two-and-a-half to three years both does justice to the depth and range of the questions that need to be addressed... and to the need to begin to draw some conclusions for the Church.
"This clearly will not satisfy everyone, but already to do a document of this size in such a time is a remarkably short period to attempt a process."
It came as the synod voted in favour of a motion calling for "conversion therapy" - aimed at altering a gay person's sexual orientation - to be banned by the government.
The private member's motion gave the Church's support to a 2015 statement by the Royal College of Psychiatrists which said the practice "had no place in the modern world".
Christian gay rights campaigner Jayne Ozanne, who introduced the motion, told the synod: "Conversion therapy is harmful, dangerous and just doesn't work.
"People may be able to alter their behaviour but they can never alter their innate desire."
During the debate, the Archbishop of York, John Sentamu, said the sooner the practice was banned, the sooner "I can sleep at night".
The synod - the governing body of the Church - is currently holding a four-day meeting in York.