Google says it is "deeply concerned" about reports that the Motion Picture Association of America and six studios led a secret campaign to attack the search giant in its fight against online piracy.

In an open letter posted to Google's public policy blog, general counsel Kent Walker wrote that he has "serious legal" concerns about the campaign, code-named "Project Goliath," in which he says the MPAA "conspired to achieve SOPA's goals through non-legislative means."

An MPAA spokeswoman responded late Thursday, calling Google “shameful” for positioning itself as a defender of free speech.

The movie studios have long considered Google the antagonist in their fight to remove pirated content from the Internet. They attempted to combat copyright infringement with SOPA, the Stop Online Piracy Act, but the legislation was ultimately postponed in 2012 after protests from companies like Google.

Even so, emails revealed through the Sony hack, reported on by The Verge and The New York Times, have shown that lawyers from MPAA and the studios — Sony, Universal, Fox, Paramount, Warner Bros. and Disney — were looking for nonlegislative ways to revive the site-blocking measures that SOPA would have put into place. Their main target in the campaign was Google, which was referred to the the emails by the name "Goliath."

"One disappointing part of this story is what this all means for the MPAA itself, an organization founded in part 'to promote and defend the First Amendment and artists' right to free expression,' " wrote Walker. "Why, then, is it trying to secretly censor the Internet?"

Google also points to reports that after the MPAA pitched Mississippi State Attorney General Jim Hood, a SOPA supporter, he sent a 79-page subpoena to Google. Although not cited in Walker's post, the Times also reported that the MPAA and the studios contributed to the campaigns of politicians, including Nebraska Attorney General Jon Bruning.

The MPAA's response called Google a facilitator of "illegal conduct" and said it would seek help from all government agencies to "protect the rights of all involved in creative activities."

Here is the MPAA's full statement.

"Google's effort to position itself as a defender of free speech is shameful. Freedom of speech should never be used as a shield for unlawful activities and the internet is not a license to steal. Google’s blog post today is a transparent attempt to deflect focus from its own conduct and to shift attention from legitimate and important ongoing investigations by state attorneys general into the role of Google Search in enabling and facilitating illegal conduct — including illicit drug purchases, human trafficking and fraudulent documents as well as theft of intellectual property. We will seek the assistance of any and all government agencies, whether federal, state or local, to protect the rights of all involved in creative activities."

Dec. 18, 3:32 p.m. Updated to include additional information about Project Goliath.

Dec. 18, 11:31 p.m. Updated to include the response from the MPAA.