AMERICAN brides are rejecting the vow to love “till death do us part” in favour of more cautious promises such as one to stay together “for as long as our marriage shall serve the common good”.

A survey by professional wedding planners estimates that barely half of this year’s 2.6m weddings will be held in a place of worship — and only one couple in five will stick to the traditional wedding script.

The rest will either “update” the wedding vows or create them from scratch, often lacing them with private jokes.

This follows a lead set by Hollywood stars such as Julia Roberts, whose handwritten vows reportedly included the pledge to “love, support but not obey” her second husband, Daniel Moder.

Traditionalists say increasingly popular phrases such as “I promise to be loyal as long as love lasts” are undermining the lifelong commitment that has been at the heart of marriage since St Paul told the Corinthians that a man and wife are bound together “unto the grave”.

Lady Diana Spencer caused some controversy when she declined to “obey” the Prince of Wales on their marriage in 1981. But in America churches have been struggling to hold the line at “till death do us part”.

“This is unconditional,” said William Donahue, president of the Catholic League for Religious and Civil Rights. “Once you change that to ‘as long as love shall last’ or similar, marriage becomes conditional and goes against the grain of the sacrament.”

Yet this is what is happening. Mary Jo Gallegos, of the Association of Bridal Consultants, which carried out the research, said that with more marriages between people of different faiths and cultures, old rules no longer apply.

“I cannot recall the last time I heard a bride promise to love unto death. People are more realistic now, especially if they are on their second or third marriage,” said Gallegos, who runs a Californian agency called An Affaire of the Heart.

Half of American marriages end in divorce, although that number has declined slightly as people opt to cohabit instead. Americans live together for three years on average before they “drift” into marriage. Yet many brides still insist on wearing white.

Sharon Naylor, the author of Your Special Wedding Vows, said she had heard vows such as “until our time together is over”. “Yet these people take the institution very seriously, especially if they are on a second marriage. They understand that you do not make a promise you cannot keep.”

Critics say the trend has been “legitimised” by celebrities such as Roberts and her fellow actress Sandra Bullock, who pledged to “love you as long as our engines last” when she married a man renowned for tinkering with racing motorbikes.

Others merely promise good manners: Will Smith, the actor, recently revealed that when he married Jada Pinkett in 1997 “our vows did not promise to forsake all others. The vow that we made was that ‘you will never hear that I did something after the fact’. One spouse will ask the other, ‘Look I need to have sex with somebody — please approve it’.”

When the actors Brad Pitt and Jennifer Aniston married in 2000, she promised to make his favourite banana milkshake while he vowed to “split the difference” over the temperature they wanted in their home. After their separation Pitt said he still considered the marriage a “total success”. “That is five more years than I made it with anyone else,” he said.

Some promise too much, said Carley Rooney, author of The Knot Guide to Wedding Vows and Traditions. “I understand why couples say ‘till death do us part’ is too gloomy, but there are an increasing number of vows that should be kept private, such as ‘I promise to remain sexually active with you’. I mean, what is going on there?” Others seek help from professional wordsmiths. Eric Shapiro, a corporate speech writer, has set up a flourishing £200 write-a-troth service.

“It’s largely brides who ask us to devise vows that sound original and poetic,” he said. “These are words they want to live by, however optimistic that may turn out to be.”

Some do not go to so much trouble. When Britney Spears, the singer, married a childhood friend in Las Vegas she chose a formula that included a promise concerning “my companion in sickness and in health”, to which she added “and in cocktails”. The marriage was annulled 48 hours later.

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