Malaysia’s Supreme Court on Tuesday upheld opposition leader Anwar Ibrahim’s sodomy conviction, maintaining a 5-year prison sentence handed out to him by a lower court last year, according to media reports. Anwar, who is reportedly the most popular opposition leader in the country, was convicted in March 2014 for having sex with a male political aide in 2008.

Sodomy and homosexuality are illegal under Malaysian laws and are punishable by a prison term of up to 20 years. Anwar has, in the past, spoken out against the harsh laws, reportedly terming them “archaic.”

Reading the verdict, Judge Arifin Zakat said there was “overwhelming evidence” against Anwar and upheld the conviction, a move that was decried by the latter as a “political conspiracy,” according to media reports.

“In bowing to the dictates of your political masters, you have become partners to the crime,” Anwar reportedly said. “I maintain my innocence. This to me is a complete fabrication coming from a political conspiracy to stop my political career.”

This is Anwar’s second sodomy conviction since he was sacked from the post of deputy prime minister in the ruling Barisan Nasional government in 1998. His previous conviction in 2000 was overturned in 2004. The latest trial investigated the 2008 allegations of sodomy against him for which he was acquitted in 2012. His acquittal was later overturned in March 2014 ahead of a state by-election in which he was reportedly expected to win.

The Supreme Court’s judgment strips Anwar of his parliamentary seat, disqualifying him from running in the country’s next general elections in 2018.

Anwar’s conviction was condemned by several human rights groups, including the Human Rights Watch, which said in a statement released after the judgment that the decision is a “major setback for human rights in Malaysia.”

“Prime Minister Najib Razak’s government has persisted in its politically motivated prosecution of opposition leader Anwar Ibrahim at the expense of democratic freedoms and the rights to non-discrimination and privacy for all Malaysians,” Phil Robertson, deputy Asia director for Human Rights Watch, said in the statement. “Allowing this travesty of justice to stand will further undermine respect for rights and democracy in Malaysia.”

However, the Malaysian government, in a statement released after the judgment, said that the country’s “independent judiciary” had reached the verdict after considering the evidence in a “balanced and objective manner.”

“In this case, exhaustive and comprehensive due process has been followed over many years. That process is now complete, and we call on all parties involved to respect the legal process and the judgment,” the government said in the statement.