What conceivable interest could British lawyers or their clients have in a pro-family “grassroots” lobbying group? And why was money also pouring in from the Choctaw Indians, a native American tribe with casinos in Mississippi?

When Pastor Chris Geeslin, then a part-time board member of the US Family Network, heard that the London cheque had allegedly come from two Russian oil barons who hoped to influence an International Monetary Fund decision to bail out the Russian economy, he did not believe it.

“That’s the way Washington works,” the group’s founder told him cynically. But it still seemed far-fetched.

Only now, as the US Congress is convulsed by its biggest scandal in generations, has the penny dropped. “I began to think, ‘Man, maybe he was telling me the truth.’ It’s incredible. I feel very angry and used,” Geeslin said.

The scandal claimed its first high-level scalp yesterday when Tom DeLay, who had already stepped aside temporarily as Republican leader in the House of Representatives, bowed to party pressure and said he would not return to the post. “I have always acted in an ethical manner,” he insisted and vowed to clear his name.

DeLay is entangled in the affairs of Jack Abramoff, a Washington super-lobbyist whom he once called “one of my closest and dearest friends”. Last week Abramoff pleaded guilty to conspiracy, fraud and tax evasion and promised to reveal details of alleged bribes to lawmakers as part of a deal with prosecutors.

Up to 20 members of Congress could be implicated. “It’s colossal,” said Alex Knott of the Center for Public Integrity in Washington. “If Abramoff discloses all of his quid pro quos, Americans will learn exactly how money has shaped their politics.”

Americans are used to lobbyists and big business oiling the wheels of their democracy, but not to “in-your-face” corruption. The fallout could be devastating for Republicans, even though Democrats also helped themselves to Abramoff’s money.

Abramoff, 47, a former Reaganite who worked his way up the corridors of power, befriending congressmen and party power brokers, was a Republican through and through. Suddenly and painfully obviously, he was also a crook.

He arrived at court wearing a trench coat and homburg hat looking for all the world like a pantomime villain. Some people remembered that when they shook his hand they felt dirty, but for years Abramoff was the man with the “moolah” — one of his favourite words — in a town that is always hungry for funds.

There was plenty of moolah to spread around. Abramoff was one of George W Bush’s vaunted “pioneers”, having raised more than $100,000 for the president’s re-election. American charities are experiencing a windfall as politicians, including Bush, rush to give away at least some of the tainted funds they received.

As for the sources of Abramoff’s money, he was not too fussy. In the 1980s he helped to lobby Congress on behalf of the Nicaraguan contras. He also took $1.5m from the white South African government and founded the International Freedom Foundation, which trained its guns on “left-wing” Oxfam for backing sanctions against apartheid.

Explore World News

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Asia News

• Africa News

• Ireland News

Times Recommends

• Transcript: interview between Nouri al-Maliki and The Times
• Golden Gate gets anti-suicide safety net
• World of Warcraft fans unite for pilgrimage