WASHINGTON — A federal judge on Wednesday refused another defense request to declare a mistrial in the corruption case against Sen. Ted Stevens, R-Alaska, instead deciding he would tell jurors to ignore disputed portions of the government’s evidence.

The ruling came after Stevens’ attorneys accused prosecutors of improperly withholding information that was favorable to Stevens and by using business records they knew were faulty to try to sway the jury. The defense has filed motions four times in three weeks asking U.S. District Judge Emmet Sullivan to either dismiss the case or declare a mistrial.

“This is a criminal case with a career on the line here,” defense attorney Robert Carey argued at a hearing. “The government has responsibilities. Time and time again, they have not lived up to them. Enough is enough.”

Stevens, 84, is accused of lying on Senate forms to conceal more than $250,000 in renovations on his cabin and other gifts from Bill Allen, the former chief of a giant oil pipeline company, Veco Corp.

Former Secretary of State Colin Powell and Sen. Daniel Inouye, D-Hawaii, could be among the first witnesses to testify today for the defense after the prosecution is expected to formally rests its case.

Prosecutors had introduced accounting records showing that a Veco worker logged hundreds of hours on the cabin project. But according to his own grand jury testimony, he was in Oregon much of that time — something the defense only learned about this week.

Though he ultimately kept the trial on track, Sullivan told prosecutors he was disturbed by the accusations and sternly demanded an explanation.

“Why is it so hard to admit that the government knew those weren’t truthful records?” he asked prosecutor Nicholas Marsh. “All along the government knew that was a lie.”

Marsh argued that the government never portrayed the business records as airtight.

Along with his decision to strike parts of the business records, Sullivan said he would instruct the jury today to ignore evidence and Allen’s testimony about what prosecutors called a sweetheart car swap: a 1964 Ford Mustang and $5,000 from Stevens for a new $44,000 Land Rover purchased by Allen.

Defense attorneys had sought to show on cross-examination of Allen that the Land Rover was worth far less, only to have prosecutors surprise them by producing a check the witness used to pay for the vehicle. The judge found the check should have been shared earlier.

Earlier Wednesday, prosecutors called an FBI agent as their last witness to introduce e-mails about the home improvements.

In e-mails from 2000 and 2001, a neighbor gave Stevens regular progress reports on a project that turned a modest backwoods A-frame into a two-story home with a new roof, hardwood floors, wraparound decks, a sauna and a garage.

“We look forward to seeing the house,” Stevens wrote back, referring to his wife, Catherine. “I guess we can’t call it a chalet anymore.”

The neighbor, Bob Persons, credited a Veco employee with doing the bulk of the work, and the senator occasionally asked for invoices.

“Don’t forget, we need a bill,” he e-mailed Allen at one point.

Prosecutors also introduced financial disclosure forms from the same period that required Stevens to report gifts to himself or immediate family.

Allen, who’s cooperating under a plea deal, testified that he couldn’t bring himself to charge his close friend for the costs, and that the senator never paid him. The jury heard secretly recorded phone conversations in which the pair discussed how to fend off the FBI.

Stevens, who spends more time at his home in Washington than in Alaska, says he paid little attention to the project that his wife oversaw. He says he assumed the $160,000 they paid for the project covered everything.

The corruption investigation has rattled Alaska politics, turning prominent state lawmakers into convicted felons and making Stevens vulnerable to a Democratic challenge for his Senate seat in the Nov. 4 election.