The Christian Institute has rejected calls to relax the rules on where people can get married.
The Law Commission has said couples should be given "more freedom" when it comes to the venue and what form the wedding will take.
It called current laws governing how and where couples can marry "outdated and unnecessarily restrictive".
At present, in order to legally marry, most couples must have their weddings in a registered building - either a place of worship or a licensed secular venue. They cannot marry outdoors, even in the garden of a licensed venue.
The Law Commission, which is consulting on the proposals, said the changes would make weddings "simpler" and "less expensive".
Simon Calvert, of The Christian Institute, disagrees with the proposals. He thinks the changes, if introduced, will lead to "trivial wedding ceremonies".
"The experience of the USA shows that 'anything goes' wedding ceremonies trivialise the marriage bond. We've all seen photos of novelty celebrity weddings splashed across our news feeds, only for the marriage to break down a few months later," he told the Express.
"Wedding vows are the most important promises two people can make to each other. There is already huge freedom to add to your vows, but there are a couple of phrases required by law to ensure the commitment is genuine and legally valid.
"Surely it's not too much to require people to formally express their intention to marry in words everyone recognises?"