She added: “The cherubs that we had got repaired with great care just a few weeks ago, have once again had their heads scythed off.
“How evil do you need to be to vandalise and destroy a child’s grave. I am devastated. We must find this person. We have informed the police. We urge anyone with details to come forward.”
It comes after a GoFundMe page in support of the replacement grave saw donations surge beyond £23,000 – allowing a temporary repair and financing a replacement headstone for the initial vandalism in February.
Ms Fergus praised the “army of heroes” who came to her aid after it was found ruined.
Two-year-old Jamie’s life was ended after the toddler was abducted by child killers Jon Venables and Robert Thompson from a Merseyside shopping centre on 12 February 1993.
The pair, who were both aged 10 at the time, were locked up following their murder convictions.
It comes as the latest bid for freedom by 43-year-old Venables is set to be heard by a parole board – the first oral hearing in more than two years, after his last appeal was rejected.
In 2023, the Parole Board rejected the bid and found he still posed a danger to children and could go on to offend again.
Venables was released on licence in July 2001 and recalled to prison in February 2010 after indecent images of children were found on his computer.
He was once again freed in August 2013 and then called back in November 2017 for the same offence, with parole judges considering his case again in September 2020.