David Cameron has warned that corruption risks fuelling terrorism as he prepared to welcome international leaders to London for a major summit on the issue.
The Prime Minister insisted he would put tackling corruption at the "top of the international agenda", warning that it was "the root of so many of the world's problems".
The summit will bring together political leaders, businesses, sporting organisations, charities and pressure groups for talks at Lancaster House on Thursday.
World leaders attending the summit include the presidents Ashraf Ghani of Afghanistan, Juan Manuel Santos of Colombia, Muhammadu Buhari of Nigeria and Norwegian prime minister Erna Solberg.
Other countries are sending less senior figures, with Russia set to be represented by deputy foreign minister Oleg Syromolotov.
Panellists at the summit are expected to include World Bank president Jim Yong Kim and IMF managing director Christine Lagarde.
The Prime Minister wants countries to sign up to a global declaration committing them to tackling corruption, ensuring it is not allowed to fester in institutions, businesses or communities and supporting people affected by it.
Mr Cameron said: "Corruption is an enemy of progress and the root of so many of the world's problems. It destroys jobs and holds back economic growth, traps the poorest in desperate poverty, and undermines our security by pushing people towards extremist groups.
"The battle against corruption will not be won overnight. It will take time, courage and determination to deliver the reforms that are necessary. But we cannot hope to solve the major global challenges we face without tackling the exploitation, fraud and dishonesty at their heart.
"For too long there has been a taboo about tackling this issue head on. The summit will change that. Together we will push the fight against corruption to the top of the international agenda where it belongs."
The summit was planned before the Panama Papers leaks revealed details of tax-dodging schemes used by wealthy individuals, political figures and companies, but the revelations have added pressure to act.
Campaigners have called for a crackdown on tax havens linked to the United Kingdom and Downing Street said it expected "a number" of overseas territories to attend.
A spokesman said: "We are in discussions with the Overseas Territories and Crown Dependencies with major financial centres about their attendance, and expect a number to join the summit."
Under the Prime Minister's plans, leaders at the summit would pledge to expose corruption wherever it is found and pursue and punish those who perpetrate, facilitate or are complicit in it.
But The Times reported that commitments included in draft versions of the summit communique had been watered down.
A passage stating there should be "no impunity for the corrupt" and "we want to make it harder for them to travel, shop and do business" was in a draft written last month, but has been deleted from the latest version, the newspaper said.
Also removed are proposed pledges to "ensure that national anti-corruption efforts are sufficiently financed from our domestic resources" and to ban corrupt companies bidding for government contracts.
A key demand that registers of the true ownership of offshore companies should be made public has been reduced to a commitment that law enforcement agencies and "those who have a need for it" can access the information.
Robert Barrington, executive director of anti-corruption campaigners Transparency International said: "The Prime Minister is creating a platform for governments that are serious about fighting corruption to make really significant changes and set the agenda for a generation to come.
"What is key now is that other governments are persuaded to sign up to ambitious targets and that the UK government does not give in to the usual last minute attempts by less committed countries to water down the summit's ambitions.
"The UK also still has some things to do to get its own house in order, for example in setting out its own comprehensive anti-corruption strategy and lifting the veil of secrecy over its own Crown Dependencies and Overseas Territories."
"It is particularly interesting that they are expecting good representation from Commonwealth countries, which could signal that under the new secretary general, who has announced that tackling corruption will be one of her priorities, an institution that has been notably absent from the global anti-corruption efforts might be about to start taking a lead."