Wikipedia announced Monday that it will now require anyone who is paid to edit articles to disclose that arrangement, in an effort to combat the practice of surreptitious advocacy on the free online dictionary.

The move, announced in a blog post, comes one week after a coalition of major public relations firms issued a joint statement vowing not to secretly edit their clients’ Wikipedia pages.

"Undisclosed paid advocacy editing is a black hat practice that can threaten the trust of Wikimedia’s volunteers and readers. We have serious concerns about the way that such editing affects the neutrality and reliability of Wikipedia,” the blog post said.

Wikipedia, which has about 80,000 volunteer editors, has long struggled with undisclosed paid editing of articles. The update to its terms of service is meant to strengthen its rules against the practice, according to its post.

An investigation begun last fall by Wikipedia’s parent company, the Wikimedia Foundation, found that several hundred accounts may have been forged by so-called “sockpuppets” — accounts meant to deceive editors about the true identities of those behind them. The fake accounts belonged to Wiki-PR, a Texas-based PR agency, which hired people to write the Wiki pages.

In another example of the problem, Wikipedia editors point to the Cyprus-based firm, Banc de Binary. The Wiki page for the firm, which has been cited for violations by the Securities and Exchange Commission, shows signs of biased writers seeking to remove mentions of the company’s problems with U.S. regulators, according to the The Wall Street Journal.

In the wake of Wikimedia's investigation, a roundtable discussion was held in February in Washington, D.C., where public relations professionals and several Wikipedia editors discussed their tenuous relationship.

As a result of that meeting, eleven public relations firms on Tuesday announced that they would end the practice of secret editing.

"On behalf of our firms, we recognize Wikipedia's unique and important role as a public knowledge resource," the firms' statement read. "We also acknowledge that the prior actions of some in our industry have led to a challenging relationship with the community of Wikipedia editors. Our firms believe that it is in the best interest of our industry, and Wikipedia users at large, that Wikipedia fulfill its mission of developing an accurate and objective online encyclopedia."

Katherine Maher, Wikimedia's chief communications officer, told the The Wall Street Journal that Monday's announced changes address a sentiment among volunteer editors: “We’re not an advertising service; we’re an encyclopedia.”