A complaint about an advertisement for popular period drama Downton Abbey that suggests homosexuality is unnatural, has not been upheld by the Advertising Standards Authority (ASA).

The magazine and newspaper advertisement for the programme, which aired on Prime, showed a picture of a servant and a member of the family he worked for.

Underneath the picture of the two men were the words: "Exclusive, servant seeks unnatural relationship".

Complainant S Ragoonanan said the advert had a "clear inference -- that a male same sex relationship is unnatural".

"I believe it is seriously offensive to label the idea of a same sex relationship as unnatural."

The advertising agency DRAFTCB, also on behalf of Sky TV, said the advertisement was designed to look like the front cover of a gossip magazine from the early 1900s.

The headline was not a comment on today's values but a reflection of the attitudes of the period the programme was set in, the agency said.

"British society's morals and values were governed by 'natural law' which was based, at that time on the teachings of the church who saw homosexuality as a sin and against the natural order."

The headline was also a comment on the "highly ingrained class system" which would view a relationship between a servant and a Duke as breaking the natural order under which society operated, the agency said.

In a majority decision, the ASA said it accepted the argument the description of the relationship was a reflection of the time in which the television series was set, and did not uphold the complaint.