Following half a dozen complaints referring to a brief lesbian kiss on Doctor Who as “gratuitous” and “inappropriate”, Ofcom has said it will not face an investigation.

The latest episode of the sci-fi series, titled Deep Breath, aired last night on BBC One to over 7 million people, in addition to special screenings in over 400 cinemas.

In the episode, Silurian lizard-woman Madame Vastra (Neve McIntosh) was forced to lock lips with her human wife Jenny Flint (Catrin Stewart) – the first time they have done so on screen.

A spokeman for Ofcom said: “Ofcom can confirm it received six complaints about a kiss broadcast in an episode of Doctor Who on Saturday 23 August.

“Having assessed the complaints, we can confirm that they do not raise issues warranting further investigation. Our rules do not discriminate between scenes involving opposite sex and same’sex couples.”

The pair have recurred on the show since 2011 and have long been portrayed as lovers.

The episode featured clockwork droids who sense life forms by their breath, with Jenny attempting to hold her breath to avoid them.

When she struggled to breathe, however, Madame Vastra helped her survive by sharing her own oxygen.

Although the episode has received a generally positive reaction from fans, some have attacked the “unnecessary” kiss and they show’s “blatant gay agenda”.

One reviewer wrote: “Found those characters that liked to display their preferences to be inappropriate for a children’s program, but the BBC seem to want to become a porn channel and are slowly edging into it.

“I think they wish to come out of the closet, well I have no objection to that if they become a private adult channel, but not on our licence fee.”

Another wrote: “I thought it was gratuitous and not particularly welcome in a family show aimed at kids. It just seems [executive producer Steven Moffat] is on some weird, lizard-lesbian perv trip.”

Last night’s episode also touched on the unconventional nature of the relationship of the pair – who live in Victorian London – with Jenny acknowledging the need to pose as Vastra’s “maid” to keep their relationship a secret.

Doctor Who has featured several prominent LGB characters, such as John Barrowman’s omnisexual Captain Jack Harkness, since its revival in 2005.

Deep Breath marked the debut of Peter Capaldi as The Doctor, taking over from Matt Smith, who regenerated during last year’s Christmas special, and made a surprise cameo in last night’s episode.

Doctor Who is set to continue next Saturday, August 30, on BBC One.