An attempt by the son of Congo's leader to stop an anti-corruption watchdog from publishing his credit card bills and company records has failed.
The president has dismissed other graft probes as racist
Denis Christel Sassou-Nguesso, who heads the state company Cotrade that markets Congo's oil, wanted them removed from Global Witness's website.
But a London High Court ruled that there was public interest in having the documents open to public scrutiny.
It said the bills implied he may have spent oil profit money on himself.
"It is an obvious possible inference that his expenditure has been financed by secret personal profits made out of dealings in oil sold by Cotrade," Judge Stanley Burnton's ruling stated.
"The profits of Cotrade's oil sales should go to the people of the Congo, not to those who rule it or their families."
The Republic of Congo is rich in oil but most of its people live in grinding poverty.
The honorary consulate of Congo in London was not immediately available for comment.
The documents on the Global Witness website include credit card bills for expensive designer items purchased in Paris and Hong Kong.
The documents originate from a Hong Kong court case involving a vulture fund seeking repayment of Congo's debts.
They showed that Long Beach, an offshore company owned by the president? son, Denis Christel Sassou-Nguesso, received payments related to two shipments of Congolese oil.
A 35-page credit card bill in Mr Sassou-Nguesso's name includes dozens of transactions relating to luxury goods, including stays at Paris's five-star Hotel Bristol and bills running as high as 13,000 euros at Christian Dior, Lacroix, Louis Vuitton and others.
That credit card bill was paid by Long Beach.
The president's son tried to bring an injunction to re-assert the confidentiality of the documents.
But the High Court judge said that under British Human Rights law there was an "important public interest" in their publication.
"Once there is good reason to doubt the propriety of the financial affairs of a public official, there is a public interest in those affairs being open to public scrutiny," Judge Burnton said.
Global Witness has welcomed the ruling which became public on Wednesday but is the result of several long court cases.
"The High Court ruling is a spectacular victory for the right of Congo's citizens to know about how public officials are managing their country's wealth and for freedom of speech in general," Global Witness Director Patrick Alley said.
"Public officials like Sassou-Nguesso should explain their financial affairs, not try to use the courts to block public debate," he said.
Last month, Congo's President Denis Sassou-Nguesso condemned a French investigation into alleged embezzlement by him and Gabon's leader as "racist" and "colonial".
He ruled Congo from 1979 to 1992, and then returned to lead the country after a coup in 1997.