By James Vicini

WASHINGTON (Reuters) - Prosecutors wrapped up their case in the corruption trial of Republican U.S. Sen. Ted Stevens on Thursday after calling a final witness who testified about his work in renovating the Alaska lawmaker's home.

Stevens, one of the most powerful Republicans in the Senate, is accused of lying on his financial disclosure forms to conceal more than $250,000 in renovations and other gifts from Alaska oil services firm VECO Corp and its former chief executive, Bill Allen.

Prosecutors called David Anderson, Allen's nephew and a welder for VECO, who said that in 2000 and 2001 he worked on Stevens' home in Girdwood, Alaska.

Anderson testified how he spent months, often joined by other VECO workers, helping to build a new first floor, a garage, and two outside decks, replace some of the windows and do a number of other projects.

He said he often worked 10 hours a day, for six days a week.

Prosecutors called Anderson to testify after the judge told the jury to disregard some VECO business records that showed Anderson had worked hundreds of hours on the project.

As a sanction for prosecutors, the judge said he would tell the jury to disregard the records because prosecutors knew Anderson actually was in Oregon for some of the time when the records showed him to be working on the house.

On at least three separate occasions the judge has sharply criticized the prosecutors for failing to turn over evidence helpful to the defense. But he has refused to dismiss the charges or declare a mistrial.

The 84-year-old senator is seeking re-election in November after 40 years in the Senate. A guilty verdict would make his re-election bid more difficult, meaning the trial's outcome could influence the Democratic Party's attempt to tighten their hold on the U.S. Senate.

Stevens has denied the charges. He said his wife took care of financial matters.

Lawyers for Stevens plan to begin presenting their defense later on Thursday. Their first witness will be Sen. Daniel Inouye of Hawaii, a Democrat. They also plan to call former Secretary of State Colin Powell.

Defense lawyer Robert Cary said as many as 10 character witnesses will be called to testify for Stevens.

U.S. District Judge Emmet Sullivan, who is presiding over the trial, said that would be too many, and that he probably would allow only four or five character witnesses to testify.

(Editing by Randall Mikkelsen and Vicki Allen)