Lea Fastow received the maximum sentence

The former Enron assistant treasurer had submitted a tax return which did not include income from her husband's secretive financial schemes.

Lea Fastow is the second former Enron officer to be convicted and will go to jail in four to six weeks' time.

The first was Ben Glisan, a former Enron treasurer.

Maximum penalty

Lea Fastow was charged last year, with six felony conspiracy and tax counts, by the US Justice Department's Enron Task Force.

However, Fastow and her husband struck plea bargains with prosecutors in January which were designed to ensure that at least one of them would be out of jail to look after their children.

But last month, a judge rejected her plea bargain, which would have seen her receive five months in jail and a further five months of confinement at home for pleading guilty to one tax misdemeanour charge.

After the plea bargain was withdrawn, prosecutors last week replaced the six original felony charges with one tax charge, and again recommended a five month prison term followed by five months of home confinement.

But US District Judge David Hittner sentenced Fastow to the maximum possible 12 months in prison, to be followed by a year of supervised release.

Government criticised

Judge Hittner said Fastow should have known what she was doing, and also criticised the government for dropping the original six charges.

"The Department of Justice's behaviour might be seen as a blatant manipulation of the federal system and is of great concern to this court," he said.

Andrew Fastow served as Enron's chief financial officer and as such supervised the company's finances.

In surrendering to federal authorities, in October 2002, Mr Fastow faced multiple charges of fraud and conspiracy to commit fraud.

He agreed to co-operate with prosecutors after his wife struck the plea bargain deal, and is set to serve a 10-year prison sentence.