Mr Rudy faces up to five years in jail and fines

Tony Rudy, ex-deputy chief-of-staff of former House Majority leader Tom DeLay, admitted to conspiring in a federal court in Washington.

Mr Rudy also promised to co-operate with an ongoing enquiry focusing on dealings of several top US politicians.

At the heart of the case is convicted former lobbyist Jack Abramoff.

Abramoff - who was sentenced earlier this week to 70 months in jail in a separate fraud case - has been co-operating in the federal enquiry.

Golf trip

Mr Rudy, 39, entered the guilty plea on one count of conspiracy.

He admitted to conspiring with Abramoff in influencing members of Congress both while working for Mr DeLay in 1995-2000 and after leaving the office.

As Mr DeLay's aide, Mr Rudy took payments from Abramoff in 2000 and also helped in stopping an internet-gambling bill opposed to Abramoff's clients, according to court papers.

After leaving Mr DeLay's office and becoming a lobbyist himself, he was involved in arranging an overseas golf trip for a Republican congressman, identified as Representative 1.

Mr Rudy faces a maximum penalty of five years in prison and a big fine.

But under the co-operation agreement, he is expected to be sentenced to lesser term.

Lavish meals

On Wednesday, Abramoff was given five years and 10 months in jail for conspiracy and fraud in the case relating to the purchase of the SunCruz Casinos gambling fleet in Florida in 2000.

But Abramoff - along with his convicted co-defendant Adam Kidan - does not have to begin serving their sentences for another 90 days in order to be able to continue co-operating in the Washington corruption case.

In January, Abramoff also pleaded guilty to defrauding the Native American tribes that were his clients, to tax evasion and to conspiring to bribe public officials.

The wide-ranging federal inquiry began in 2004 after reports that he and business partner Michael Scanlon had received some $45m (£26m) from Native American tribes with casinos.

Abramoff was accused of exploiting the tribes to enrich himself and his friends, and offering politicians in both houses of Congress lavish meals, tickets to major sporting events and trips.