Kerry Needham, 42, has written a message on her website asking for anyone who believes they might be Ben to get in touch, and telling her son that she loves him.
Ben, from Sheffield, vanished on July 24 1991 after travelling to the Greek island of Kos with Mrs Needham and his grandparents. Over the years there have been a number of possible sightings and a range of theories about what happened to the youngster, who would now be 25.
The message, which is also translated into Greek on the Help Find Ben Needham website, reads: “This is a direct appeal to anyone who is around 25 years old and possibly living with a family who you look nothing like. I beg you to get in contact with me. I promise to cause no problems for your family who you live with, I just want you to know the truth about what happened to you and to know you are healthy and happy.
“A simple DNA sample can be taken from you without causing any distress to anyone. So if you think you were born in 1989 and you have blue/grey eyes and a possible birthmark on your leg, YOU could be Ben!!!
“Twenty-three years have gone by Ben and I love you just as much today as I did the day you were born. Please anyone get in touch and end all this pain your family feel living without you.”
Last month, the Home Office agreed to fund a team of British detectives to help search for the youngster after Ben’s family engaged human rights barrister Ian Brownhill to help them.
South Yorkshire Police asked for the financial help to follow up information the family believe has never been properly investigated.
The funding is for the financial year from April 2015 and is for up to £700,000. Ben’s family have said they want South Yorkshire Police to investigate leads, including a file they have handed in that lists eight sightings from unconnected people.
The Home Office backed a South Yorkshire Police operation in 2012 when land was excavated on Kos, near where Ben went missing.
No trace of the boy was found. Last year, a DNA test on a young man featured in video footage shot in Cyprus proved to be negative.