A fall in voter numbers may be tied to the growth in wealthy donors giving to political parties, an expert warned amid the launch of a new report into dirty money’s influence on politics.

Anti-corruption group Transparency International UK called for new light to be shed on the influence of big money on British politics, which it claimed has contributed to a “crisis point” for a lack of faith in the system and dwindling participation in elections.

Speaking at the launch of the campaign group’s latest report into dodgy donations, Parth Patel of the Institute For Public Policy Research suggested there was a “combined story here between falling turnout and the growing concentration of donations”.

“Turnout is falling in the long run, and that should be setting off more alarm bells than it actually does. Where the hell are all the voters going?” he said.

Voters see that the “returns on voting are declining”, he said, adding: “We are quickly approaching that tipping point where elections lose legitimacy because the majority didn’t take part.”

Transparency International’s report warns that some £115 million donations reported by political parties between 2001 and May 2024 have come from “unknown or questionable sources”, while £48.2 million has come from donors who have bought privileged access, influence or honours.

Donors involved in corruption, fraud or money laundering have given £42 million to British political parties, the group said, warning there is an “absence of real deterrent” from breaking the law around donations.

It called for lower spending limits for political parties during elections and leadership contests to end an “arms race” on donations.

Labour peer Dame Margaret Hodge told the audience at the event she wanted to see a new lower threshold for parties to declare any donations to the Electoral Commission.

Donations of more than £11,180 – whether from and individual or company – must currently be declared to the commission, whether these are in a single sum or spread out across a year.

Dame Margaret suggested even the sources of small donations of a few hundred pounds should be named and declared in order to “maximise transparency”.

Transparency International also recommended the Government brings forward an Elections Bill, to prevent cash from unknown origins entering British politics.

In its election manifesto, Labour promised to “restore confidence” in Government with new ethics commission ensuring ministers are upholding standards, and in politics more widely by “strengthening the rules around donations to political parties”.