Image copyright AP Image caption Dennis Hastert is the longest-serving Republican House speaker in US history

Former US House of Representatives speaker Dennis Hastert has been charged over illegal cash withdrawals to pay hush money to an unnamed individual.

Mr Hastert, 73, allegedly withdrew $1.7m (£1.1m; €1.6m) in small amounts to skirt federal reporting rules.

According to the indictment, he agreed to pay $3.5m to an unnamed individual to "conceal his prior misconduct".

He served as a Republican congressman from Illinois for more than 20 years until 2007.

'Individual A'

The indictment alleges that Mr Hastert, who is also charged with lying to the FBI, made a deal in 2010 with "Individual A" to make payments in recompense for unspecified prior misconduct.

Individual A lives in Yorkville, Illinois, where Mr Hastert was a high school teacher and wrestling coach between 1965 to 1981, and has known the former speaker most of his life.

According to the indictment, Mr Hastert began by making $50,000 withdrawals and passing the cash to Individual A every six weeks.

As a result of federal rules that require banks to report withdrawals of more than $10,000, the former speaker being questioned by his bank.

Thereafter, the indictment says, Mr Hastert made a series of $10,000 withdrawals in an attempt to avoid detection.

'I kept the cash'

When questioned by the FBI, Mr Hastert said he was withdrawing the money because he did not trust the bank.

"Yeah... I kept the cash. That's what I'm doing," he said.

By the time the charges were announced on Thursday, he had paid about half agreed sum of $3.5m, the indictment says.

Each of the two charges against Mr Hastert carries a maximum penalty of five years in prison and a $250,000 fine.

He could not be reached for comment.

After losing the job of speaker in 2006 and resigning from the House of Representatives in 2007, Mr Hastert joined the Washington law firm Dickstein Shapiro as a senior adviser.

The Chicago Mercantile Exchange said on Thursday that he had resigned from the law firm's board.