Mr Wilson and Ms Plame say the White House went after them
US President George W Bush intervened in July to prevent Lewis "Scooter" Libby, former chief of staff to Vice-President Dick Cheney, from serving a 30-month jail term.
Libby had been convicted of lying about the disclosure of CIA officer Valerie Plame's identity.
The case took a new turn when on 21 November the former White House spokesman Scott McClellan said in an extract from a forthcoming book that the president and vice-president were involved in efforts to mislead the public.
What did McClellan say?
He said that when he had told reporters in 2003 that neither Libby nor Karl Rove, a senior Bush aide, was involved in the leak "it was not true". He alleged he had been misled by "five of the highest ranking officials in the administration... Rove, Libby, the president's chief of staff [Andrew Card] and the president himself".
The White House said that it was unclear what McClellan meant and no further details of the book have been made available yet.
What was Libby convicted of?
Libby was found guilty of two counts of perjury (lying to a grand jury), one count of making a false statement to the FBI and one of obstruction of justice. He was not charged with leaking the CIA officer's identity.
He was found not guilty on a separate count of making a false statement to the FBI.
Could he have got a longer sentence?
He could have got up to 25 years, but the prosecution asked for a maximum of three. Mr Libby himself asked the court for clemency, saying:
"It is respectfully my hope that the court will consider, along with the jury
verdict, my whole life."
US District Judge Reggie B Walton said: "People who occupy these types of
positions, where they have the welfare and security of the nation in their hands,
have a special obligation to not do anything that might create a problem."
Libby was also fined a quarter of a million dollars.
President Bush, however, described the 30-month prison sentence as "excessive".
The president's decision falls short of a full pardon - Libby will still have to pay the fine and faces a period of probation.
What did Libby do wrong?
Libby was convicted of lying to FBI investigators and the grand jury about how and when he learned that Valerie Plame was a CIA officer, and lying about disclosing classified information to reporters.
He told investigators that he had learned about Ms Plame from reporters - but he had already been told about her by other government officials, including Vice-President Cheney.
Libby's defence was that any untrue statements he had made were the results of his poor memory - that if he had known about Ms Plame earlier than he said he had, he had genuinely failed to remember that fact.
But juror Denis Collins said the jury found it "very unlikely" Libby could have forgotten such a key detail when it had been part of nine conversations he had had in the days before he said he learned it afresh.
What is the significance of the trial?
The trial exposed the inner workings of the White House in the summer of 2003, when questions were being raised about the invasion of Iraq.
President Bush had said before the war that Saddam Hussein had tried to buy ingredients for a nuclear bomb from a country in Africa.
But a man sent to investigate that claim - former US ambassador Joseph Wilson - said he had found no evidence of it, and wrote an opinion piece in the New York Times criticising the Bush administration's use of intelligence to justify the invasion.
Shortly after, a newspaper columnist, Robert Novak, revealed that Mr Wilson's wife, Valerie Plame, was a CIA agent tracking nuclear proliferation.
Deliberately revealing an agent's name is a serious offence in the US and the leak sparked a high-level criminal inquiry.
Mr Wilson and his wife accused leading White House figures of taking revenge on him by "outing" his wife.
No-one was ever charged with the original leak, but Libby was charged with perjury and the obstruction of justice.
So who was the source of the leak?
In September 2006, former state department official Richard Armitage admitted that he was responsible for the original leak.
Mr Armitage said his revelation to two journalists - Novak and Washington Post reporter Bob Woodward - had been "a terrible mistake", one which he had made inadvertently, not knowing Ms Plame's job was secret.
At the time, the Washington Post said in an editorial that "one of the most sensational charges levelled against the Bush White House - that it orchestrated the leak of Ms Plame's identity to ruin her career and thus punish Mr Wilson - is untrue".
Why did Mr Armitage keep quiet for so long?
He says he told Patrick Fitzgerald, the special prosecutor investigating the affair, in 2003 that he might have been the source for the Novak article. He says Mr Fitzgerald told him not to say anything.
Some people are now asking why Mr Fitzgerald pursued others in the case with such determination. Others reply that Mr Armitage's admission does not mean other administration figures were not involved in an attack on the Wilsons.