The Church of England has called on the government to drop proposals to extend the period for which terrorism suspects can be held without charge.
Synod members said ministers had not produced sufficient evidence
Ministers have published plans to increase the maximum detention period from the current 28 days to 42.
The Church's ruling body, the General Synod, said the move would disturb the "careful balance" between individual liberty and national security.
A motion was supported by 235 out of 244 synod members meeting in London.
Dr Philip Giddings, of Oxford, who presented the motion, said he was aware the government was in a difficult situation but that there was no compelling evidence in favour of change.
"So far the 28-day limit has proved sufficient. The government suggests that soon it might not be," he said.
"Clearly it is difficult to draw a hard and fast line. Hard cases make bad law.
"Four weeks is already a considerable disruption of the life of an innocent person, and his family. Six weeks would be even more oppressive."
Dr Giddings said terror suspects could be subject to continued surveillance or control orders as an alternative to custody.
An amendment to the motion, proposed by Bill Nicholls, of Lichfield, for a senior High Court judge to review the holding of terror suspects on a weekly basis was rejected by the synod.
The Archbishop of York, Dr John Sentamu, said the government had not produced sufficient evidence of the need for an extension to the 28-day limit.
The motion also raised concern over the US detention camp at Guantanamo Bay, restrictions on individuals under British terror laws, and the use of control orders on suspects.
Dr Giddings said it was widely agreed that the detention camp at Guantanamo Bay had been "an affront to legal principle and human dignity".
A review of control orders which "may border on house arrest" should be carried out, he added.
Earlier, the synod debated Gordon Brown's suggestion that senior clerical appointments should be made by the Church and not the prime minister.
The Archbishop of Canterbury, Dr Rowan Williams, said: "I can see no positive persuasive argument for leaving prime ministers with the ability to set aside the preferred candidate of those to whom the Church has entrusted this work to become an archbishop or diocesan bishop."
Meanwhile, the Anglican Church in Uganda has said it will boycott the Lambeth Conference in protest at invitations being sent to bishops who condone active homosexuality.
The Archbishop of Canterbury will convene the meeting of the world's Anglican bishops, held once every 10 years, in July.