The BBC and Channel 4, former employers of British actor and comedian Russell Brand, said on Sunday they were investigating claims of rape, sexual assaults and emotional abuse over a seven-year period, which the 48-year-old has denied.

Four women have alleged sexual assaults between 2006 and 2013, when Brand was at the height of his fame working as a presenter for BBC Radio 2, Channel 4 and acting in Hollywood movies, a joint media investigation said on Saturday.

The broadcasters BBC and Channel 4, along with the production company Banijay UK, said on Sunday that they would open internal inquiries into the claims.

"We are urgently looking into the issues raised," a BBC spokesperson said.

The allegations were made in a joint investigation by The Sunday Times, the Times and Channel 4's Dispatches.

"Banijay UK has launched an urgent internal investigation and will cooperate with any requests for information from broadcast partners and external agencies," the production firm said.

According to the Times investigation, several women have made a range of accusations about Brand's alleged controlling, abusive and predatory behaviour.

In a video released on Friday, Brand denied the "very serious criminal allegations."

He said he had received letters from a TV company and a newspaper listing "a litany of extremely egregious and aggressive attacks."

"Amidst this litany of astonishing rather baroque attacks are some very serious allegations that I absolutely refute," he said in the video clip posted online.

According to the media reports, one woman alleged that Brand raped her in his Los Angeles home, while another claims he assaulted her during a three-month relationship while she was 16 and still at school.

Known internationally as the former husband of pop star Katy Perry, Brand began his career as a stand-up comedian in the early 2000s.

He was the host of the chat show Big Brother's Big Mouth, a spin-off of the popular reality series, for three years from 2004.

He also played rock star Aldous Snow in the 2008 film "Forgetting Sarah Marshall" and its 2010 sequel "Get Him To The Greek."

London's Metropolitan Police said that while it was aware of the allegations, "At this time, we have not received any reports in relation to this."

"If anyone believes they have been the victim of a sexual assault, no matter how long ago it happened, we would encourage them to contact police," it said. (AFP)