Communications watchdog Ofcom has launched an investigation into whether an episode of reality show Big Brother breached the broadcasting code when swearing was heard before the watershed.

The episode, shown on Channel 5 on August 7, was one of dozens that attracted complaints from viewers who protested about issues including bad language, the show’s voting system and animal welfare.

An Ofcom spokesman said: “Ofcom is currently investigating the broadcast of offensive language before the watershed in an episode of Big Brother on August 7th.

“After carefully assessing viewer complaints about the rest of the series, Ofcom did not consider they raised issues warranting investigation under our rules.”

The show, which started out on Channel 4 but is now on Channel 5, has run into trouble before.

In 2005, it was criticised for operating ”at the limits of acceptability” after showing scenes in which two contestants appeared to have sex in the pool while another simulated sex with a wine bottle.

Two years later, Ofcom said Channel 4 was guilty of ”serious editorial misjudgment” after thousands of viewers complained about the alleged racist bullying of Indian actress Shilpa Shetty by housemates Jade Goody, Danielle Lloyd and Jo O’Meara.