A poster claiming that gay people want to "abolish the family" has been criticised by the advertising watchdog.
The advertising watchdog said the CCTV's advert was inaccurate
The Christian Congress for Traditional Values (CCTV) advert showed a man, woman, boy and girl with the statement "Gay aim: abolish the family".
The Advertising Standards Authority (ASA) said the organisation could not stand up the claim that it was likely to cause serious or widespread offence.
CCTV defended its concerns about a perceived threat to Christian values.
The ASA upheld complaints against the ad, ruling that it could be inflammatory.
The poster broke advertising rules on social responsibility, decency, matters of opinion and truthfulness, the ASA said.
A complainant had said the advert did not accurately represent gay people's views and was offensive.
The watchdog said that a modern family was increasingly less likely to include a married man, woman and their children.
"We considered the statement and the way it appeared was likely to cause offence both to the mainstream gay community and supporters of equality," said an ASA spokesman.
The ASA added that it was also "likely to be seen as controversial and possibly inflammatory by a significant number of people who saw the poster in an untargeted medium.
"We concluded that the poster was likely to cause serious or widespread offence and might lead to anti-social behaviour."
The CCTV, which describes itself on its website as an alliance of Christians but not a church organisation, was instructed to make sure future campaigns would not be offensive.
The group defended the poster, citing gay organisations' manifesto documents from the 1970s which described the traditional family unit as working against homosexuality.