The Archbishop of Canterbury, Dr Rowan Williams, has intensified the Church's attack on the Government's Gambling Bill and said that it will endanger the vulnerable.
Dr Williams has met senior ministers to voice his concerns that a proliferation of "super casinos" will increase debt and problem gambling.
The Archbishop's views add weight to a cross-denominational campaign against the plans and will irritate Tony Blair, who is struggling to reassure his backbenchers.
Dr Williams has told friends that he believes the controversial legislation to be driven more by commercial considerations than public need.
He fears that if new casinos are allowed to spring up there could be a "domino effect" across the country, which would lead to a "downward spin" in parts of society.
The Archbishop's warnings are echoed in an unpublished Church of England briefing paper, which says that the Bill in its current form "threatens serious personal and social damage".
"We respect the right of adults to entertain themselves as they choose but vulnerable people, including children, should be protected from opportunities for high-value gambling that outstrip their self-control," a spokesman said.
"The Government should proceed cautiously with the Bill, increase safeguards against irresponsible use and ensure rigorous monitoring of the impact of legislation."
Criticism of the Bill, which has been spearheaded by the Methodist Church and the Salvation Army, was also joined yesterday by the Roman Catholic Archbishop of Cardiff, the Most Rev Peter Smith.
"What the Government seems to be saying is we want to reform the law, reduce crime, and protect children and the vulnerable. That's marvellous," the Archbishop told Radio 4's Today programme.
"But then they propose these huge casinos, which will have unlimited numbers of machines, which will be open perhaps for 24 hours, and it is then the vulnerable adults who can be caught in this, and the social effects of obsessive gambling are dreadful."
The Archbishop said he was unimpressed by Tessa Jowell, the Culture Secretary, who said that the opposition to the casinos was tainted by a "whiff of snobbery".
He said: "I think that was rather ridiculous. It is nothing to do with snobbery or elitism. It is a genuine concern.
"There wasn't, in my mind, a great call for this from the public in general. And I think, to an extent, the Government has misread the public mood on this.
"I hope the Government will listen to the genuine concerns expressed through people's MPs."