Republican lawmakers are accusing bankrupt solar-energy firm Solyndra of breaking its promise to have executives testify before a congressional panel, and have released a Sept. 10 email in which a company lawyer said the CEO would "appear voluntarily and answer the committee's questions." 

The email appeared to back up GOP claims Tuesday night that the company was "reneging" on written assurances to testify. The company announced late Tuesday that the two executives set to appear before a House Energy and Commerce subcommittee on Friday would plead the Fifth and refuse to answer questions on the advice of counsel. 

"It's their legal right, we respect that," Rep. Cliff Stearns, R-Fla., chairman of the subcommittee, told Fox News. "But we still have many questions that someone should answer sometime soon." 

In a joint statement, Stearns and full committee chairman Rep. Fred Upton, R-Mich., questioned whether the company was "trying to hide" something. 

The email from Sept. 10 showed the company two weeks ago assuring the committee that CEO Brian Harrison was ready for his congressional close-up. 

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"Brian Harrison will appear voluntarily and answer the committee's questions on any day the committee chooses, beginning next week," the email said. "He will appear without any need to issue a subpoena." 

While Harrison and Chief Financial Officer Bill Stover are expected to show up, Solyndra made clear Tuesday they will not be entertaining questions. A statement said they could not provide "substantive answers" to lawmakers' questions due to the ongoing Justice Department probe. 

"Present circumstances require both gentlemen to exercise their Fifth Amendment rights in the face of questioning that might occur," the company said. 

The company's statement said both executives were following the advice of counsel, and it continued to defend the firm's actions. The company came under scrutiny after filing for bankruptcy despite receiving nearly $530 million in federal taxpayer-backed loans. 

"The company is not aware of any wrongdoing by Solyndra officers, directors or employees in conjunction with the DOE (Department of Energy) loan guarantee or otherwise," the statement said, claiming the investigation will "clarify the facts surrounding the events leading to the DOE loan guarantee to Solyndra and looks forward to a time when its executives can more freely discuss their views on these events." 

Stover attorney Jan Nielsen Little also wrote in a letter to committee members that, "on my advice," Stover would show up at the hearing but not offer testimony. "Nothing of substance should be read into Mr. Stover's decision to heed his counsel's advice," Little wrote. 

Another attorney submitted a similar letter on behalf of Harrison, writing: "While I have instructed my client not to testify at the hearing, it would be a mistake to infer anything from this other than that is the act of a prudent lawyer who is newly engaged to represent a witness in ongoing government investigations." 

The GOP committee leaders weren't convinced. 

"It's disappointing that the officials who canvassed the halls of Congress in mid-July and misled our members about the financial state of their company are now unwilling to answer direct questions, but any effort to cover up the truth will ultimately not succeed," they said. 

Another letter released by the committee Wednesday showed the Solyndra CEO assuring Energy and Commerce members in July about the financial health of the company. The letter said revenues were "projected to nearly double" in 2011. 

"Solyndra is an example of a U.S. company using American innovation and ingenuity to compete in the global solar market," Harrison wrote. 

After the company filed for bankruptcy earlier this month, officials claimed global competition -- particularly from China -- flooded the market with solar panels and eroded Solyndra's financial standing. 

Meanwhile, pressure is growing on Solyndra and the administration officials involved in the loan to provide more information. 

The chairman of the House Oversight and Government Reform Committee said Tuesday that his panel will probe government loan programs that benefit private companies in light of the scandal. 

Rep. Lamar Smith, R-Texas, chairman of the House Judiciary Committee, has called for a special prosecutor in the Solyndra case.