LONDON (Reuters) - More than half the money donated to groups campaigning in Britain’s EU membership referendum was given by 10 individuals or companies, according to research published on Friday, raising questions over the outsize influence of the wealthy on politics.

Anti-corruption campaign group Transparency International UK also said 95 percent of donations to the ‘Leave’ and ‘Remain’ campaigns in the run-up to the June 23 Brexit vote were made by only 100 donors.

“The debate around the biggest question we have faced in a generation was financed by an astonishingly small group of exceptionally wealthy donors. That’s a dangerous place for any democracy,” said Duncan Hames, Transparency International UK’s director of policy.

“It illustrates the general dependency of our country’s political parties on a millionaires club of some 50 donors, many of whom also sit in the House of Lords,” he added in a statement, referring to parliament’s upper chamber.

Transparency International said public trust in politics was falling, with 76 percent of respondents to a poll run by the group saying wealthy individuals were using influence on government to benefit their own interests and 28 percent saying most or all members of parliament were involved in corruption.

It said the two largest donors in the Brexit vote were David Sainsbury, the former chairman of the supermarket Sainsbury’s, who donated 4.2 million pounds ($5.32 million) to Remain between January and June, and stockbroker Peter Hargreaves, who gave 3.2 million to the Leave campaign.

The third-largest donor, a group called Better for the Country which donated 2.1 million pounds to Leave, had not declared the source of its income, Transparency International said.

Britons voted to leave the EU by 52 percent to 48 percent, launching the country into its biggest constitutional shift since World War Two and resulting in downgrades to its economic outlook.

Transparency International recommended a cap on political donations of 10,000 pounds per donor per year, as well as tighter rules over declaring and companies donating.

It said one-sixth of reported donations to political parties since 2001, or 125 million pounds, were made by companies.

Current rules do not limit the size of donations but require political parties to declare large sums.

Britain was rocked in 2006-07 by a “cash for honors” scandal when police investigated allegations that the then ruling Labour Party had rewarded some donors with appointments to the House of Lords. No charges were brought.