Britain has frozen assets belonging to James Ibori, a former governor of Nigeria's Delta State and a financier of the Nigerian president's electoral campaign, according to diplomatic sources.
Monday's move is one of the strongest so far by the UK to aid the fight against corruption in the poverty stricken, oil-producing state.
"Ibori's properties and some of his assets have been restrained," the Reuters news agency reported an unnamed diplomatic source as saying.
Delta State is one of Nigeria's three oil-producing states, rich in resources but where corruption has meant there is little to show for the money.
Ibori's tenure as governor ended on May 29 and Nigeria's state governors lose their immunity from prosecution when their term's end.
Last Thursday, Southwark Crown Court in London granted a police application to freeze assets worth 17 million pounds ($35m).
Nigerian media reported over the weekend that the assets included properties, cash and a private jet.
There was also speculation that the British move against Ibori would be a prelude to his arrest and prosecution in Nigeria.
Changing attitudes
Ibori has close ties to the presidency.
He accompanied Umaru Yar Adua, elected as Nigeria's president earlier in the year, on almost every stage of his electoral campaign and bankrolled much of it.
If Ibori is arrested in Nigeria, how the new president reacts is likely to be seen as a test of his stance on corruption.
Ibori is the third Nigerian governor to fall foul of British law since a new Proceeds of Crime Act was introduced in 2002.
Previously, two former governors were charged with money laundering but both jumped bail.
Britain, Nigeria's former colonial ruler, has for decades been a popular destination for Nigerian politicians buy properties and send their children to study in private schools.
British police have worked closely with Nigeria's anti-corruption Economic and Financial Crimes Commission (EFCC), created in 2003, and the British crackdown is seen as a reflection of changing attitudes within Nigeria.
Under Olusegun Obasanjo, Nigeria's former president, the EFCC was widely criticised for targeting his opponents but leaving his friends undisturbed.
Since Obasanjo handed over power to Yar Adua in May, the EFCC has begun prosecuting five former state governors, raising hopes that Yar Adua intends to crack down on corruption.