Jane Onyanga-Omara

USA TODAY

LONDON — Secretary of State John Kerry told an international summit here Thursday that corruption is as great an enemy as extremism.

Leaders from around the world gathered in London for the one-day meeting aimed at fighting corruption hosted by British Prime Minister David Cameron.

'I’ve been shocked by the degree to which I find corruption pandemic in the world today," Kerry said.

“Corruption writ large is as much of an enemy, because it destroys nation states, as some of the extremists we’re fighting,” he added.

He said the United States was working to restore $350 million stolen by generals in Nigeria and sent to the U.S. back to the west African country.

The summit aims to get leaders of nations, business and civil society to agree on measures to expose corruption, punish perpetrators, support the people affected and to “drive out the culture of corruption wherever it exists,” the British government said.

Nigerian leader not seeking apology over ‘corrupt’ comments

“Corruption is the cancer at the heart of so many problems we need to tackle in our world,” Cameron said at the meeting.

He said that eliminating corruption is “about not just changing laws and practices. It’s about changing culture.”

Britain announced Thursday that it will lead a new international network to stamp out corrupt practices. At least 18 countries have signed up to partner with each other to share best practices. The government said the process of awarding public sector contracts will also be visible to the public for the first time by October.

British companies must now disclose who benefits from their ownership, and foreign companies that own property in Britain must declare their assets.

The summit hit global headlines before it even began after Cameron was overheard telling Queen Elizabeth II that Nigeria and Afghanistan were "fantastically corrupt."

"We've got some leaders of some fantastically corrupt countries coming to Britain... Nigeria and Afghanistan, possibly the two most corrupt countries in the world," Cameron said at an event at Buckingham Palace on Tuesday.

Panama Papers: What we know now

Cameron later said Nigeria and Afghanistan had made “remarkable steps forward” against corruption. Nigerian President Muhammadu Buhari said he did not want an apology, but wanted the return of stolen Nigerian assets held in British banks.

The summit comes amid the international fallout from the Panama Papers scandal, when an anonymous source known only as “John Doe” leaked 11.5 million documents in April from the Panama law firm Mossack Fonseca, which specializes in creating accounts to hide financial dealings. More than 100,000 companies were registered to the British Virgin Islands.

The International Consortium of Investigative Journalists, which has handled the Panama Papers, released to the public a massive database with more than 360,000 people and companies associated with offshore accounts earlier this week.

Several Crown Dependencies — self-governing islands affiliated to the U.K. — and British overseas territories were named in the documents.

In 2013, Cameron told lawmakers: "I do not think it is fair any longer to refer to any of the Overseas Territories or Crown Dependencies as tax havens. They have taken action to ensure that they have fair and open tax systems."

Mark Goldring chief executive of the anti-poverty organization Oxfam GB, said the summit "has shone a welcome light on the problem of corruption," but said Cameron had failed to "lift the veil of secrecy surrounding the U.K.'s own tax havens."

"Until tax havens are required to publish public registers showing who really profits from shell companies, the corruption and tax dodging revealed by the Panama Papers will continue undisturbed and millions of people in both the U.K. and the world's poorest countries will pay the price," he said.