The way in which police dealt with concerns about a four-year-old boy who was eventually starved to death by his mother and left to decompose in his cot is to be investigated by the police watchdog.

The Independent Police Complaints Commission (IPCC) has announced it is examining West Yorkshire Police's conduct in relation to the death of Hamzah Khan, whose body was found in a cot at his home in Heaton, Bradford, in 2011, almost two years after he died.

Mother-of-eight Amanda Hutton, 43, was jailed for 15 years last year after she was found guilty of Hamzah's manslaughter and neglecting five of her other children.

At her trial it emerged that a range of agencies, including police officers, had contact with her family but no-one spotted the danger the children were in.

The IPCC said it is now investigating West Yorkshire Police's handling of concerns raised about Hamzah's welfare.

It said allegations of neglect had been made to West Yorkshire Police and other agencies prior to the discovery of the youngster's body and it had contacted the force to ask for details of complaints to police that have been reported in the media.

The commission said it will examine what action West Yorkshire Police took after concerns about Hamzah's welfare were raised. It will also look at why the matter was not referred to the IPCC in 2011.

IPCC Commissioner Cindy Butts, who will oversee the investigation, said: "The death of Hamzah Khan was a truly shocking example of the most cruel neglect imaginable and at the heart of it lies the loss of a young life.

"Our investigation will examine what action West Yorkshire Police took and also why the contact was not referred to us in 2011."

Detective Chief Superintendent Andy Brennan, head of West Yorkshire Police Professional Standards, said: "West Yorkshire Police referred this matter to the IPCC in November last year and they have decided this will be an independent investigation which we will fully support and assist in any way we can."