South Africa's opposition has rejected claims that President Jacob Zuma cannot be prosecuted while he is in office. Democratic Alliance leader Helen Zille has gone to court in a bid to overturn a decision to withdraw corruption charges against Mr Zuma. But his lawyers say he cannot be prosecuted unless he is either impeached or resigns. The charges were dropped in April, shortly before elections which saw Mr Zuma becoming president. State prosecutors said there had been evidence of political interference in the case under the previous government, led by Mr Zuma's rival Thabo Mbeki. Mr Zuma has always denied the charges. Ms Zille said she will oppose the submissions made by Mr Zuma's lawyers to the Pretoria High Court this week. A paragraph in the president's legal submission to the court stated: "Charges can only be brought if he is successfully impeached in terms of the Constitution or after his term of office ends," reports the Mail and Guardian newspaper. But Ms Zille is adamant that this statement is not true, saying South Africa's constitution did not exempt a sitting president from criminal prosecution. She added that the constitution was based on the principle that all all are equal before the law. Mr Zuma later refused to comment on his lawyers' submissions but said he would appear in court if ordered to do so. Ms Zille said the DA is going to court to reinforce the doctrine of "separation of powers" and wants Mr Zuma charged in his personal capacity. Mr Zuma was first charged with corruption, racketeering and money-laundering in 2005, but has never faced trial. The National Prosecution Authority (NPA) had obtained recordings of phone conversations which suggested the timing of the decision to charge Mr Zuma in 2007 had been manipulated, leading to the charges being dropped. Charges were resumed just days after Mr Zuma won a bitter contest against Mr Mbeki to lead the ruling African National Congress. Source: BBC