Lincolnshire Police has referred itself to the police watchdog after a two-year-old boy was found starved to death alone next to his father who had suffered a fatal heart attack over Christmas.
Bronson Battersby's body was found with his father Kenneth's at their home in Skegness on 9 January.
The little boy had been under children's services care, and a social worker got in touch with his father on 27 December and arranged a visit for 2 January - but there was no answer.
They made enquiries at other addresses where the child could be and contacted the police, according to Lincolnshire County Council.
The social worker went back to the home on 4 January, but again was met with no response and alerted the police.
On 9 January the social worker was given access to the property by the landlord - where the father and son lived alone - and the tragedy was discovered.
The police force said in a statement: "The exact actions of organisations involved will be analysed in a forthcoming review and at this stage it would be inappropriate to comment further.
"As part of standard procedures we have referred this to the Independent Office for Police Conduct (IOPC) as a result of a death or serious injury following police involvement."
'His body was too fragile to hold'
Bronson's mum Sarah Piesse, who last saw him before Christmas, told The Sun: "I can't believe it.
"They can't let them get away with this. We have to be able to rely on social workers to keep our children safe."
She said she couldn't hold her son when she went to identify him.
"I couldn't pick him up because his body was too fragile," she said.
"I could only touch him. He had been left there too long."
She said the post-mortem results showed "Bronson starved to death because his dad died".
"They think Kenneth died no earlier than December 29," she said.
"It means if the social worker had pushed to get in when she got no reply on 2 January then Bronson would still have been alive."
Heather Sandy, executive director for children's services at Lincolnshire County Council, said: "This was a tragic incident, and we are supporting the family at this difficult time.
"We are currently carrying out a review of the case alongside partner agencies to better understand the circumstances, and we await the results of the coroner's investigations as well.
"Our thoughts are with the family and friends of those involved."
Bronson would normally be paid a visit at least once a month, according to the council.
The social worker involved is not suspended but has taken time off following the traumatic experience.
Father and son were 'inseparable'
A neighbour, who didn't want to be named, told Sky News the father and son were like "two peas in a pod".
"Bronson was a gorgeous, happy little boy who just wanted cuddles and his dad was his best friend - they were inseparable," she said.
She added she had last seen the pair on Boxing Day on their way to the shops in town. They'd waved and had "big smiles".
On 27 December she said she sent a text message to the dad to check on him as she was worried about his health.
He replied: "Thank you both for caring about me and Bronson means the world to us it really does."
On New Year's Day, she sent another message wishing them a happy new year - but received no response.
Toddler died in 'heartbreaking circumstances'
A Lincolnshire Police spokesperson said earlier: "Police were made aware of the deaths of a 60-year-old man and a two-year-old child at a property in Prince Alfred Avenue, Skegness, at around 3.25pm on Tuesday, 9 January.
"Investigations have been carried out and the deaths are not being treated as suspicious.
"The matter has been passed to the coroner's office."
Sir Keir Starmer paid tribute to the toddler in the House of Commons on Wednesday.
"I can't let today pass without saying how saddened I was by the tragic death of Bronson Battersby, aged just two, who died in heartbreaking circumstances in Skegness," the Labour leader told MPs.
"I know that this House will join me in sending our deepest sympathies to his family."