The reality, Mr Benda says, is 'the Japanese courts thumb their noses at these legal obligations'.

Brian Thomas, 62, who also helped to found the CRC, moved to Japan from South Wales in 1988, two years after meeting his wife, Mikako. Their son, Graham Hajime, was born in January 1990, but Mr Thomas has not been permitted to see him since April 1993, when the marriage ended. He carries his son's photo with him at all times.

'Japan is still living in the feudal age and children are seen here as little more than chattels. And the authorities here have absolutely no idea of the psychological impact that it is having on thousands of children,' says Mr Thomas. 'My own mother has gone blind now, so she will never be able to see her grandson.'

He believes that the Japanese government discriminates against foreign mothers and fathers when it comes to custody, or even access, to children of international marriages. '[Graham] has never met his cousins and probably does not know that he has relatives in Britain,' Mr Thomas says. 'Every Christmas and every birthday, I send presents or money, and a card. Sometimes they are sent back, sometimes not.

'I do not know what he has been told about me, but I am not leaving Japan. He is paramount, and when he comes looking for me, I intend to be here so I can look him in the eye and tell him that I never left him; I never walked away.'

It is a fact of life in any society that marriages break down; it is even harder to make a relationship work in marriages between people of different ethnic, linguistic and cultural backgrounds. In 2006, 33,701 marriages involved a foreign national wedding a Japanese, and an estimated 20,000 children are born to mixed-nationality couples here every year.

The United States is dealing with 47 cases of US children being abducted to Japan. There are 30 cases involving Canadian citizens, and British officials admit to dealing with 10.

Shaikh Akhtar Ali met a Japanese woman, Junko, travelling in Calcutta and they married in 1990, when Mr Ali was 26. Junko returned to her parents' home in the city of Suwa, in northern Japan, and gave birth to a daughter, Najima, the following year. Their son, Anis, was born in 1995, but the marriage broke down and in 1999 they divorced.

Mr Ali has tried to remain in touch with his children, but in seven years he has seen them only three times. The last time he met Najima and Anis, he exchanged e-mail addresses and they were able to stay in touch. But in March, the Japanese e-mail account was deactivated, the family phone number is no longer in service - and Junko said in a message that the children do not want to hear from their father.

'I do not believe my daughter is not willing to speak to me,' Mr Ali says. 'I used to carry her on my shoulders into the fields, to catch dragonflies and butterflies for her pet box. We used to swim together.'

Lawyers in Japan are too expensive for Mr Ali, and he has little faith in his own government to bring about a resolution. Physically a long way away from his children, he has nowhere to turn, and confesses: 'I am very sad.'

Mr Ali's case is far from uncommon.

Even though Mr Benda remained legally married and shared equal custody of his two children, it took him 3? years just to find out where they were living after they were abducted by his wife. No Japanese authorities would help locate them or provide information about their health or school situation.

In vain he approached the local police, the Tokyo Metropolitan Police, the local city office, the Health and Welfare Ministry, schools and education officials, the US embassy, Interpol and various other organisations set up to assist foreigners in Japan. He was forced to approach authorities in the US, have his children registered as missing and have an international arrest warrant for kidnapping issued against his wife.

'Parental abduction is not even considered a crime in Japan when it is done while the parents are still married, except in rare circumstances, when the foreign parent is the abductor,' says Mr Benda, pointing to the 2000 case of Dutch national Engel Nieman.

Arrested at Osaka port as he was about to board a boat leaving Japan with his two-year-old daughter, Nieman was charged with kidnapping the girl with the intent of trafficking her into the sex trade. Nieman had been trying to take her back to the Netherlands so her terminally ill grandfather could see her one last time. It is the vast difference between how Japan treats its own nationals who abduct children, and how foreigners are dealt with, that really rankles with those who have lost contact with their offspring.

'I have pursued custody and visitation rights through the Japanese courts twice now, each time appealing my case all the way to the Japanese Supreme Court,' says Mr Benda. 'I have never been granted a single scheduled visit with my daughters.'

In the US, the Justice Department has indicted his former wife under the International Parental Kidnapping Act, as the girls are US citizens being retained overseas while his parental rights are being denied. The Japanese government, however, refuses to recognise the charge and will not take any action on the extradition request. 'I feel very angry and misled by the Japanese legal system,' Mr Benda says. At the root of the problem, CRC of Japan believes, is that Japanese judges do not have very strong enforcement authority in family law cases. And a more fundamental issue is Japanese nationalism, says Mr Benda. He says Nieman was imprisoned for kidnapping his own daughter - a statute Japan has never used against its own citizens.

Yet there is small ground for optimism for parents who have been forcibly estranged from their sons and daughters in Japan. A group of non-profit organisations and volunteer associations there have allied themselves with parents' groups from around the world and enlisted the support of Japan's bar federation and politicians from various political parties.

In May, the Justice Ministry announced it was starting a review of domestic laws on child abduction and that the Hague Convention could be signed by 2010.

'I'm a born optimist,' says Mr Thomas. 'I have to keep my spirits up. If I didn't, it would be very easy to slip into depression, like other parents have done already ... I feel sure that one day my son will want to know who his father is and where I am. And when we find each other, I'll welcome him with open arms.'