A Malaysian opposition party has filed a civil lawsuit against Prime Minister Najib Najib Razak offences for alleged election offenses involving $700m in his bank accounts.

The anti-corruption agency recently announced the money, most of which was received ahead of March 2013 general elections, came from donations and not from state investment fund 1Malaysia Development Berhad (1MDB).

1MDB, whose advisory board is chaired by Najib, and which has debts of more than $11bn, is under investigation for corruption and financial mismanagement. The affair has triggered a political crisis for Najib.

The People's Justice Party said the money was 26 times above the amount that Najib's ruling National Front coalition was allowed to spend in the elections. The National Front, which has ruled since independence from Britain in 1957, won the elections but lost the popular vote for the first time to an opposition alliance that includes the People's Justice Party.

The party's vice president Nurul Izzah Anwar said the lawsuit will reveal "all kinds of bribes and corrupt tactics" allegedly used by the National Front to win the elections.

With evidence of corrupt transactions, she said the results of the 2013 general elections should be nullified and new polls should be called.

"The fact is that the alleged amount spent by Najib far exceeds the allowable amount for elections," she told the Reuters news agency.

The party also named 1MDB, the Election Commission and Adnan Mansor, the secretary-general of Najib's ruling Malay party, in the lawsuit.

Government officials couldn't be immediately reached for comment.

The 1MDB crisis has partly contributed to the Malaysian currency crashing to four ringgit to the dollar on Wednesday, the lowest since the 1997-98 Asian financial crisis.

Source: Agencies