The former governor of a Nigerian oil state pleaded guilty in a British court on Monday to laundering millions of dollars in a rare case of a Nigerian politician being held to account for the corruption that blights Africa's most populous nation.

London hailed the case of James Ibori, a prominent power-broker in Nigeria's ruling party, as a major victory in the British justice system's efforts to stop corrupt foreign politicians laundering stolen funds via UK channels.

Ibori is a household name in Nigeria after two terms as governor of impoverished oil-producing Delta State from 1999 to 2007. He is used to being addressed as Your Excellency and courted by crowds of people seeking his patronage.

It was a different scene on Monday at Southwark Crown Court in London, where Ibori sat in the dock behind a glass partition as prosecutor Sasha Wass described his tenure as a time of wide-scale theft, fraud and corruption.

There was effectively a thief in the government office of Delta State, Wass told the court.

Ibori pleaded guilty to 10 counts of money laundering, fraud and related offences. He pleaded not guilty to a further 13 similar charges. Sentencing will take place in April and Ibori remains in custody. His assets will be confiscated.

Among other crimes, Ibori admitted that he had conspired with others to pocket $37 million that should have gone into Delta State coffers from the sale of shares it owned in the telecoms company V Mobile.

Britain's Department for International Development (DFID) said all funds recovered through the confiscation of Ibori's assets would be given back to the people of Delta.

Ibori ... lived a life of luxury after he embezzled what the (police) estimate to be $250 million of Nigerian public funds - equal to $38 from every person living in the state at the time of his crimes, the department said after the court hearing.

At the time of his arrest, he had been trying to buy himself a private jet worth $20 million.

His case has enormous resonance in Nigeria, Africa's biggest oil producer, where a small ruling class enjoys a jet-setting lifestyle while most of the 140 million Nigerians live in poverty with little or no access to power, health or education.

Ibori stepped down as governor of Delta, one of three big oil-producing states in the volatile region, after two terms because the law did not allow him to seek a third one.

He then established himself as a behind-the-scenes kingmaker in the ruling People's Democratic Party.

This is a wake-up call to those in office now - manage public funds prudently or corruptly enrich yourself and go to jail, said Omenazu Jackson, of the opposition African Renaissance Party, who lives in Rivers, another oil-producing state in the Niger Delta.

Those in public office should know that they are temporary managers of a collective estate and will be required tomorrow to give account of their stewardship, he told Reuters by phone.

LIED HIS WAY INTO PUBLIC OFFICE

In court on Monday, Ibori waved and smiled at supporters who crowded into the room, but spoke only to identify himself and enter his pleas.

Wass said he had lied about his date of birth when running for election in 1999 in order to hide the fact that he was already a convicted criminal. He had falsified his date of birth on his passport and other official Nigerian documents, she said.

He lied his way into public office. He tricked the Nigerian authorities and the Nigerian voters. He was never the legitimate governor of Delta State, Wass told the court.

Ibori had been expected to face a 12-week trial involving dozens of witnesses, but after he entered his guilty pleas the prosecution said that he had in effect accepted the substance of the case against him and a full trial was no longer necessary.

The charges to which he pleaded not guilty had not been dropped and would remain on file, Wass said.

Ibori's wife, sister and mistress have already been convicted of helping him launder money in separate trials in London, but media had not previously been allowed to report on those convictions in order to avoid prejudicing Ibori's own case.

Nigeria's own anti-corruption agency, the Economic and Financial Crimes Commission (EFCC), had tried to prosecute Ibori after he stepped down as governor and lost the immunity he had enjoyed while in office.

But the EFCC's efforts to go after Ibori and other powerful politicians were hampered by what campaign group Human Rights Watch called political interference, institutional weakness and inefficiency in the judiciary.

Instead, Ibori was arrested while on a trip to Dubai in May 2010 at the request of British police and was extradited to Britain in April 2011. Monday's guilty pleas are the culmination of a seven-year inquiry into his affairs by British police.

The successful prosecution of Ibori will be a relief to British investigators who were thwarted in their 2005 attempt to bring to trial another oil state governor suspected of money laundering, Diepreye Alamieyeseigha.

Then governor of Bayelsa State, which neighbours Delta and also produces oil, Alamieyeseigha was charged with money laundering in London but he jumped bail and escaped back to his country dressed in women's clothes.

(Additional reporting by Austin Ekeinde in Port Harcourt)