An increasingly vocal number of Christians are attacking what they say is a "war on Christmas" by those determined to enforce a rigorously neutral holiday season reflecting America's constitutional separation of church and state.

Earlier this month, the official greetings card sent out by the president and first lady stirred up controversy for omitting any reference to Christmas.

It has been 13 years since the last presidential card explicitly mentioned Christmas - in deference to other holidays at this time of year, like Hanukkah - but this didn't deter the critics.

"The Bush administration has suffered a loss of will and... they have capitulated to the worst elements in our culture," fumed William Donohue, president of the Catholic League for Religious and Civil Rights.

Some 80% of Americans describe themselves as Christian, and about 96% celebrate Christmas.

Millions of them use the phrase "happy holidays" as a convenient way of showing respect for other faiths.

Yet the row over the White House card has been just the tip of the iceberg in a year when the battle against secularism is being fought harder than ever by religious conservatives.

'Secularists gone wild'

One leading home improvement chain removed references to "holiday trees" from all its stores after being criticised by the American Family Association.

The AFA and other groups are urging members to petition dozens of other major retailers that they accuse of stripping Christ from Christmas with phrases like "happy winter".

The campaign against "secularists gone wild" is also being driven by people like John Gibson, a popular anchor on the Fox News Channel.

His book - The War on Christmas: How the Liberal Plot to Ban the Sacred Christian Holiday is Worse Than You Thought - collates examples of how political correctness is, he says, neutering "America's favourite holiday season".

Meanwhile, at least 1,500 lawyers have volunteered to sue any town that tries to keep nativity scenes out of its holiday displays.

About 8,000 public school teachers stand ready to report any principal who removes Silent Night from the choir programme.

Such moves reflect the 1985 US Supreme Court "reindeer ruling".

It said that town-square nativity scenes and the like were constitutional if balanced with secular symbols like Santa Claus, thus avoiding the appearance of state-endorsed religion.

'Well-organised extremists'

The American Civil Liberties Union is an active defender of the religious freedoms guaranteed in the constitution, and is often the target of conservative ire over the issue.

This week, Fran Quigley, head of the ACLU in Indiana, hit back with an editorial entitled: "How the ACLU didn't steal Christmas."

He said the group was being demonised by well-organised "extremists" whose real agenda was to crush religious diversity, "and make a few bucks in the process".

"Nowhere in the Sermon on the Mount did Jesus Christ ask that we celebrate his birth with narrow-mindedness and intolerance, especially for those who are already marginalised and persecuted," he wrote.

He said the ACLU's mission for justice saw it work hard to protect the rights of free religious expression for all people, including Christians.

It is not a stance that cuts much ice with people like Jennifer Giroux, co-founder of Operation: Just Say "Merry Christmas".

Her group has tapped into a current craze for rubberised wristbands, producing a green and red version emblazoned with the slogan "Just say 'merry Christmas'".

What began as a local campaign has swiftly mushroomed.

She has already sold 15,000 bracelets at $2 each. A further 43,000 are on their way to customers.

"We just wanted to encourage Christians to have the courage to say 'merry Christmas' instead of 'happy holidays'," she says.

"We had no idea that it would tap into a national frustration.

"People are tired of being told not to celebrate Christmas, they are tired of the ACLU. This is just parents saying they want to preserve Christ in Christmas."