Lobbying groups have long relied on traditional advertising to get their messages out to the broader public. Now one of Washington’s most powerful organizations has discovered a new medium: film.

This week, a documentary called “InJustice,” which attacks America’s class-action lawsuit system, began airing on the cable television ReelzChannel. The film was bankrolled in part by the U.S. Chamber of Commerce’s legal arm, which has long lobbied for tort reforms more favorable to corporations.

The release of “InJustice” comes at the same time that another movie about the civil-justice system, “Hot Coffee,” has taken the documentary world by storm. The film, which argues that civil lawsuits help protect consumers, premiered at the Sundance Film Festival in January and is now airing on HBO.

Unlike “InJustice,” “Hot Coffee” was not produced with direct help from a big advocacy group. But the American Association for Justice, the main lobbying group for trial lawyers, has helped bolster publicity for the film, including a $10,000-per-sponsor screening held as part of the group’s annual convention last weekend.

The dueling documentaries provide another example of the myriad ways that trade groups, lobbying firms and other advocates try to advance their causes in Washington and across the country. From wrapping buses in advertisements to waging viral Twitter campaigns, political advocacy groups are constantly pushing for new strategies to reach supporters.

“We thought it was an important issue that was really suited to this kind of approach,” said Harold Kim, senior vice president of the chamber’s Institute for Legal Reform, referring to “InJustice.” “The vision was aligned with the general philosophy of ILR.”

Chamber officials declined to say how much the organization paid toward the documentary. But filmmaker Brian Kelly said in an interview that the amount exceeded $100,000.

Kelly, who runs the Single Malt Media television documentary company, said that he came up with the idea of a film about lawsuit abuse several years ago but that it was a hard sell for regular television channels. The chamber eventually agreed to the concept while granting him full artistic control.

“This is something new and different,” Kelly said. “With the way cable and broadcast television has evolved, I think there’s a real chance this will become more common.”

For movies that focus on the civil-justice system, the two films couldn’t be more different. According to the film’s Web site, “InJustice” provides “a shockingly candid look-under-the-hood of the American legal machine,” part of “an epic journey through the dark corridors of lawsuit scams and abuses” allegedly perpetrated by trial lawyers.

“Hot Coffee,” by contrast, bills itself as an expose of how corporate America has “used anecdotes, half-truths and sometimes out and out lies” to “put limits on people’s access to the court system.” The movie takes its name from an infamous lawsuit about spilled McDonald’s coffee that became the butt of jokes nationwide — but which filmmaker Susan Saladoff portrays as an egregious case of corporate negligence.

The American Association for Justice says it has no direct ties to the film. But Gary M. Paul, the group’s president, said the documentary provides a useful counterweight to pro-business propaganda.

“For years, incredibly well funded corporations and organizations like the U.S. Chamber have led a campaign to try to undermine the civil justice system,” Paul said in a statement. “ ‘Hot Coffee’ provides an incredible opportunity to debunk myths and educate people about these issues.”

It’s fair to say that “Hot Coffee” has gotten the better reviews. In addition to a warm reception at Sundance, reviewers have called it “a stunning debut” (The Washington Post), a “scalding takedown” (the Daily Beast) and “an eye-opening indictment” of big business (Variety).

The scattered reviews for “InJustice” have been mixed: The Above the Law legal blog compared it to an “infomercial,” while conservative magazine publisher Steve Forbes called it “riveting” and “fascinating.”

Perhaps not surprisingly, ChamberPost — the business group’s blog — liked it very much. “After more than two years in the making, the result is a truly compelling story,” a chamber official wrote.