In a letter to chief constable Simon Parr last December Ruth Neave said she was appealing to him since “though I was found not guilty of his murder it seems to me that you have failed in many respects”.

She claims that police never took notice of two young boys “who as good as admitted their involvement in his murder, even after a newspaper boy reported seeing them in that area.

There was also a report of a young boy being assaulted a few months earlier and in the same area “but this was neither investigated properly or the possible links to Rikki’s death considered”.

She also reminded Mr Parr that social services lost numerous files concerning her and her family’s background and these only came to light after Rikki’s death.

Ruth wants an explanation as she believes they are relevant to any inquiry into Rikki’s death.

After Rikki’s death, social services went into meltdown. Jobs were lost, files were mislaid or disappeared and even now, 20 years later, she believes within those files could be clues as to who did kill her son.

A decision to re-open the case was considered in 2005 but Ruth says she was never contacted even though her solicitor had been informed and it was only from talking to a friend she found out that inquiries were ongoing.

“Because of advances in DNA testing I want the pair of Rikki’s socks still in the hands of police to be checked with the national DNA database,” she said.

“Also with advances in obtaining fingerprints then the partial fingerprint can be lifted and checked against that same database. I was told it was not possible to do it but maybe today it is.

“All I ask is for justice for my son and answers to the questions I am asking.”

A police spokesman said: “We have examined the information passed to us. However, there is insufficient evidence to reopen the investigation.”