DHAKA (AFP) - The eldest son and heir apparent of former Bangladeshi premier Khaleda Zia has been so badly tortured while in custody on graft charges he may be permanently crippled, his lawyer alleged Monday. Tareque Rahman has serious back pain and "neither can he stand up nor he can sit down for more than three minutes," his lawyer Rafiqul Islam Mia said, quoting a medical report. Rahman, who is joint secretary of the Bangladesh Nationalist Party (BNP), has been detained since March last year on graft charges after the government launched a nationwide anti-corruption crackdown. Although he did not have a ministerial role in his mother's government, the 42-year-old was frequently referred to as the most powerful man in Bangladesh during Zia's second tenure as prime minister between 2001 and 2005. Mia, his lawyer, told an anti-graft court late Sunday that Rahman had been energetic and fit before he was arrested, but was now unable to appear in court because of "severe physical problems." "He has already made a statement to the court saying he was tortured mercilessly and in the most inhumane way while he was on remand. As a result, he is now physically impaired," Mia said. "The lower part of his body may be crippled permanently if he is not treated properly. Doctors have suggested that he should be sent to the United States, England or Germany immediately for proper treatment," he said. During a court appearance Monday, Zia blamed the government for the poor health of her two sons and demanded authorities send them abroad for treatment. "When they (sons) were arrested they were in good health, they walked to the courts. Now they can't and the government is responsible for this," the private news agency UNB quoted her as saying. Her youngest son, Arafat Rahman, who has also been detained on graft charges, is suffering from acute asthma and lung problems. He also appeared in court Monday, arriving in an ambulance, and faces charges in the same case as his mother. "If the government is neutral, they (her sons) must be sent abroad," Zia said, referring to the release last week of ex-premier and Awami League party leader Sheikh Hasina Wajed who was allowed to fly to the US to treat hearing problems. The comments come a day after Rahman's wife and daughter appealed to the country's home minister for his release on humanitarian grounds. In a letter they urged the government to allow him to travel overseas for treatment. A government minister told AFP Sunday that plans were underway to free Zia so she can have treatment for arthritis and knee problems. But Zia ruled out going abroad for the treatment of arthritis and knee problems. "I've told you before and am also telling you now that I will not go abroad leaving the people in this worrying situation," she said. The government, which came to power in January 2007 after emergency rule was imposed and elections cancelled, made the move to ensure participation of the two parties in polls in December. Both the BNP and Awami League, who ruled the country for 16 years before the army-backed government took over, had said they would boycott the government's democracy talks and the elections unless their leaders were released.