A highly decorated US Marine says a manager at defence contractor BAE Systems called him "mentally unstable" and alleged he had a drink problem.
Sgt Dakota Meyer, 23, is suing BAE for defamation for comments made after he was critical of planned sales of advanced sniper scopes to Pakistan.
He was awarded the Medal of Honor, the highest US military accolade, for saving 36 lives in Afghanistan.
BAE told the Wall Street Journal it "strongly disagreed with his claims".
A spokesman said, though, that the firm wished him "success and good fortune in his endeavours".
Sgt Meyer was the first living Marine awarded the Medal of Honor since the Vietnam War.
'Doing my part'
In a court filing in San Antonio, Texas, Sgt Meyer says a supervisor maliciously made "false and defamatory" remarks and that he interfered with his prospective employment "without legal justification".
The supervisor, Bobby McCreight, became hostile towards Sgt Meyer after the former Marine expressed his disapproval of BAE's attempts to sell advanced thermal optic scopes, the filing says.
After leaving Ausgar Technologies, another defence contractor, in March 2011, where he trained soldiers on optical equipment, Sgt Meyer had taken a position with BAE.
"This is where I could see me still 'doing my part' for the guys who are in the same situation now that I was in 18 months ago," he wrote in an email to Mr McCreight included in the court filing.
But selling scopes to Pakistan that Sgt Meyer said were more advanced than those used by US troops did not sit well with him, who had served near the Afghanistan-Pakistan border.
"We are simply taking the best gear, the best technology on the market to date and giving it to guys that are known to stab us in the back," he wrote.
Pakistan has long been accused of harbouring militants in its tribal areas and of not doing enough to ensure that US and international troops in Afghan border regions are safe from insurgent attack.
A spokesman for BAE told the Wall Street Journal the US state department made final decisions on whether to sell defence equipment to Pakistan.
It is not known whether the scopes were ever sold to the country's military forces.
Sgt Meyer's lawsuit alleges that Mr McCreight "berated and belittled" him after he objected to the sale.
Mr McCreight mocked his Medal of Honor nomination as "pending star status" and took exception when he went on a business trip for a more senior boss.
"May I remind you whom [sic] works for who [sic]? You report to me, not Jerry or Vadim [the division president]," Mr McCreight wrote.
In an attempt to resume his old job at Ausgar, Sgt Meyer contacted his former supervisor, who told him there was likely to be an opening in his team.
However, after Sgt Meyer resigned from BAE in May 2011, Sgt Meyer received an email from an Ausgar supervisor that said the firm would not be rehiring him.
Bob Higginson, a manager who needed to approve the hiring, had been contacted by Mr McCreight, Sgt Meyer says.
According to a copy of the email included in the court documents, Mr McCreight had told him that the marine was mentally unstable, was not performing his duties and had problems with social drinking.
Through a lawyer, Sgt Meyer declined to comment on the case, but is seeking damages.