Six monitor makers have been accused of belonging to a global price-fixing "cartel" in a new class-action lawsuit in the US.

The lawsuit, filed in a California court on behalf of Nathan Muchnick, alleges that Chunghwa, LG Electronics, Matsushita, Philips Electronics, Samsung and Toshiba artificially inflated the prices of CRT monitors to remain stable despite a rapid decline in demand.

CRT prices should have fallen as technologically superior products were introduced, said Joseph Saveri, a lawyer with Lieff Cabraser Heimann & Bernstein, which represents Muchnick.

"Instead, for almost a decade, we have seen periods of unnatural and sustained price stability, as well as inexplicable increases in the prices of CRTs," Saveri said.

The complaint alleges collusion by the manufacturers, causing the plaintiff and direct purchasers to overpay for CRT monitors. The suit seeks triple damages.

Of the 48 million monitors that will ship this quarter, 9 percent are expected to be CRTs, down from 13 percent last year, according to projections by DisplaySearch, a research firm. The average selling price of CRT monitors has increased to $32 in the fourth quarter, up from $30.80 last year, said John Jacobs, an analyst at DisplaySearch.

The price increase could be explained by factory closures. CRT factories have been closing down because of LCD penetration, and the reduced manufacturing capacity makes it hard for suppliers to meet demand, Jacobs said.