US campaign finance rules, which have allowed wealthy individuals to pour millions of dollars into the 2012 presidential election, have shaken public confidence in the political process, according to a report by the Global Commission on Elections, Democracy and Security.

The commission, which is headed by former UN secretary general Kofi Annan, and comprises former world leaders and Nobel prize winners, has identified a rise in "uncontrolled, undisclosed, illegal and opaque" political finance across the world as a key threat to electoral integrity, in a new report due to be launched in the UK on Friday.

The report singles out the US as an example of a country where lack of transparency and controls in political finance have left it struggling to restore the public's confidence in its elected officials to act in their interest.

The commission blamed a series of court decisions – in particular the controversial Citizens United ruling, which turned campaign finance reform on its head and spawned Super Pacs, effectively removing barriers to corporate and union spending to influence elections

Citizens United has "undermined political equality, weakened transparency of the electoral process and shaken citizen confidence in America's political institutions and elections", the report said.

It also criticises US states which have sought to introduce voter identification laws and other measures that have the effect of suppressing African American participation in the political process.

Vidar Helgessen, secretary general of International Institute for Democracy and Electoral Assistance, said that US system was cited as just one example of flaws in democracies worldwide. But, he said the US, as the most powerful nation in the world, had a responsibility to set an example.

"If a vast majority of citizens say the systems is undermining political equality and weakening transparency of the electoral process, then there is an issue of trust in the government," he said.

Political finance was an important issue which had not received the attention and reform it deserved, he said.

"We are seeing increasing inequality and we are in a global economic recession and it is an issue that will only grow. It is not only in new and emerging democracies that provide challenges and have elections that lack integrity"

The report cited a national survey this year by the Brennan Center for Justice at New York University law school, which found a majority of people believe nominally independent Super Pacs to be a danger to democracy.

"Nearly two-thirds of Americans said that they trust government less because big donors have more influence over election officials than average Americans," the report said.

It concluded that, although Super Pacs must disclose their contributors and may not coordinate directly with candidates by law, in practice, "both constraints have been flouted".

It compared the US unfavourably to Canada, which has faced many of the same campaign finance struggles and concludes: "In contrast to the USA, Canada has managed to strike a balance between safeguarding individuals speech and protecting the overall integrity of the electoral process."

It argued that the rise of "uncontrolled political finance" was one of five major threats to democracy, which could rob it of its unique strengths to promote political equality, the empowerment of the disenfranchised and the ability to manage societal conflicts peacefully.

The report looked at a host of problems, including post-election violence in places such as Kenya and Nigeria, illicit finance in Costa Rica, and disenfranchised populations in Europe.