The makers of FarmVille and Words With Friends seem to be testing the K Street waters.

Zynga — a San Francisco-based social network game developer — LinkedIn, Mozilla and Twitter waded into a Washington policy debate on Tuesday for perhaps the first time as part of a coalition of Internet companies opposing legislation intended to crack down on websites selling counterfeit goods.

None of the four companies have their own registered lobbyists, but they have joined forces with a group of increasingly visible Internet companies, including Google, eBay and Yahoo, to oppose proposals gaining momentum in both the House and Senate.

“These folks aren’t known to have had a presence in D.C. until this legislation,” said Andy Halataei, the director of government relations at the Information Technology Industry Council. “I guess this bill got their attention.”

In joining the fray, the technology companies also are picking a fight with one of Washington’s most stalwart lobbying powers, the U.S. Chamber of Commerce.

For months the chamber has waged an aggressive lobbying and advertising campaign in support of a bill introduced in May by Senate Judiciary Chairman Patrick Leahy (D-Vt.) that would authorize the Justice Department to file a civil action against foreign websites “dedicated to infringing activities.” House Judiciary Chairman Lamar Smith (R-Texas) and ranking member John Conyers (D-Mich.) introduced a companion bill in the House last month.

The idea of the legislation is to prevent websites based overseas from selling imitation versions of American products such as golf clubs or medication.

But the law would place a new burden on search engines, requiring them to block these suspect sites from showing up in results. It would also make it illegal for Internet service providers to connect users to the flagged sites.

The chamber’s efforts have irritated some of its members who oppose the idea.

Last month, Yahoo left the organization, which has long been known as the most powerful advocate for business interests in Washington. Google is “frustrated” with the chamber’s advocacy, and while it has no immediate plans to leave the organization, a person familiar with the company’s thinking said it would not be out of the question. EBay, also a member of the chamber, has not publicly discussed concerns with the chamber’s position on this legislation.

While the chamber remains the top lobbying force in Washington, young Internet companies such as Google and Yahoo are lining up their own muscle on K Street — spending millions more than ever on lobbying even as other industries pull back, according to a recent analysis by the Center for Responsive Politics. Facebook, which set up a political action committee earlier this fall, has spent $910,000 on lobbying in the first three quarters of 2011 — four times more than it did by this point in 2010. Google, which has spent nearly $6 million on lobbying this year, spent only about two-thirds that during the same period in 2010. And Twitter, known for hosting debates and White House town halls, has four staffers in its steadily expanding Washington office, though they do not lobby.

“I think people’s first read of this is that it is hard to know how or when they would be in compliance even if they make a good faith effort,” Halataei said. The industry council has not yet taken a public stance on the proposal.

“We support the bill’s stated goals — providing additional enforcement tools to combat foreign ‘rogue’ websites that are dedicated to copyright infringement or counterfeiting,” the Internet companies wrote in Tuesday’s letter. “Unfortunately, the bills as drafted would expose law-abiding U.S. Internet and technology companies to new uncertain liabilities, private rights of action and technology mandates that would require monitoring of websites.”

A spokesman for the chamber declined to comment on the letter because it involved members who oppose the chamber’s official position.

“It is great that everyone agrees that rogue sites have no place in a legitimate online marketplace,” said Steve Tepp, chief intellectual property counsel for the U.S. Chamber of Commerce.

The chamber-led coalition in support of the bill includes Walmart, Eli Lilly & Co. and Netflix. Google and other opponents of the legislation argue that restricting the Internet in the U.S. sets a bad international precedent and that the language defines infringing too broadly. Other opponents, including Sen. Ron Wyden (D-Ore.), who has put a hold on the bill, argue that it will restrain online commerce and that it is the first step to censoring the Web.

Sources familiar with the state of play said the Senate could take up the proposal sometime after Thanksgiving. Google executives are set to testify before the House Judiciary Committee in a hearing addressing the House proposal today, but the politics are tough with two major California constituencies — Hollywood and Silicon Valley — facing off.