DHAKA (Reuters) - A Bangladesh court sentenced the acting head of the main opposition party to life in prison on Wednesday and 19 other people to death over a plot to assassinate Prime Minister Sheikh Hasina in 2004, lawyers said.

The ruling against Tarique Rahman, who was tried in absentia as he is living in exile in London, dims the future of his Bangladesh Nationalist Party (BNP) ahead of the South Asian nation’s next election in December.

The BNP has been in disarray since Rahman’s mother and former prime minister Khaleda Zia were jailed on corruption charges in February, while Rahman sought to run the party affairs from London.

The case related to an attack on a rally that Hasina was addressing in the capital Dhaka when she was in the opposition and Khaleda, her bitter rival, was in power.

Minutes into Hasina’s speech, assailants threw grenades that killed 24 people and wounded more than 500, most of them workers with her then-opposition Awami League party.

Judge Shahed Nur Uddin ruled the attack was a “conspiracy” mounted by the BNP to wipe out the Awami League leadership, lawyers quoted him as saying in the courtroom.

Deputy Attorney General Motahar Hossain said the BNP engaged members of militant group Harkat-ul Jihad al-Islami to carry out the attack targeting Hasina and her top colleagues.

The court held that the conspiracy was plotted in Rahman’s personal office with militant leaders in attendance.

The BNP said the charges were trumped up. “The judgment was not given in a just way, so we will go for appeal and we believe all of them will be freed without any charges,” BNP lawyer Sanaullah Mian told reporters.

Mosharraf Hossain Kazal, a lawyer for the government, said it would go to the Supreme Court to seek the death penalty for Rahman and his party colleagues who received lesser sentences.

The court convicted 49 people in all on Wednesday and sentenced 19 to death including ex-junior home minister Lutfuzzaman Babar. Eighteen of the 19 are in custody.

The court decision was the latest blow for the BNP, many of whose members are in prison.

“It is a disaster for the BNP, as its de facto chief has been implicated as the main planner and handed lifetime in prison,” said Ataur Rahman, a professor of political science at Dhaka University. “There is not enough time for them to be able to absorb this debacle.”

The BNP has not spelled out its plans for the election but has called for a neutral caretaker government to be put in place before the vote. A similar demand before the 2009 election was rejected, prompting the BNP to boycott those polls.

The BNP has also urged the government to free Khaleda, jailed for five years in February on a corruption conviction.