Economic uncertainties and fears over job security are making workplaces more competitive, sparking rivalries between co-workers for pay raises and promotions, a new survey shows.

According to OfficeTeam, a Menlo Park, Calif.-based staffing services firm, half of 150 executives recently surveyed said co-worker competition is on the rise, including about 10 percent who said it has skyrocketed in the past decade.

"In an uncertain economy, people grow more concerned about job security and proving their worth to employers," Dave Willmer, executive director of OfficeTeam, said in a statement. "This pressure to perform may result in rivalries between employees."

Only three percent of executives surveyed said they felt workplaces were becoming less competitive.