The family of John-Paul Mokulou, who was visiting relatives during a holiday to Nigeria, believe he is being held hostage by the country's junta in an attempt to lure his father who they want to question.
The boy's mother, Christine Olukoya, has flown from Britain to Nigeria in an attempt to secure the release of her son.
Glenda Jackson, the Labour MP who represents the family who live in Hampstead, north-west London, yesterday condemned the Nigerian authorities' actions as "outrageous and unacceptable".
John-Paul, who was born in Britain, was arrested by Nigerian security forces on 23 April while he was staying with his father in the capital, Lagos. His father, who escaped during the raid, is believed to be a cousin of the former president of Nigeria and may be seen as a threat to the existing regime.
The boy is being held in a Nigerian Special Security Services secure complex in Lagos. At first the authorities denied to relatives and the British Consular officials that John-Paul, who has dual nationality, was being held. However they have since confirmed his existence but have refused to allow anyone to see him.
They are convinced he is being held hostage to try and force his father to give himself up.
The Commonwealth last month agreed to tightening sanctions until General Sani Abacha's military Government shows greater respect for human rights.
Ms Jackson said: "John Paul is a 13-year-old British schoolboy, travelling on a British passport, and there can be no excuse for his abduction and continuing imprisonment.
"I urge the Foreign Office to do everything in it's power to secure his immediate release."
Malcolm Rifkind, the Foreign Secretary, has been informed about the case and consular staff are believed to be involved in behind the scenes negotiations.
A Foreign Office spokesman said yesterday: "Although [John-Paul] holds dual nationality, we have pressed hard for consular access to see him on a number of occasions, since he is a minor.
"We are concerned about his welfare. However the family have told us that further intervention may be detrimental."Reuse content