UPDATE 2-Publicis plunges after shock fall in revenue

* Almost 2 bln euros wiped off firm’s market value

* Publicis Q4 revenues well below forecasts

* Shares of rivals also dragged lower (Adds analysts, details, background, updates shares)

PARIS, Feb 7 (Reuters) - Publicis shares plunged as much as 15 percent on Thursday after weaker than expected fourth quarter revenues cast doubt over the company’s ability to offset a decline in its traditional advertising business with new consultancy work.

The shares were on track for their biggest one-day drop since 1992, wiping almost 2 billion euros ($2.3 billion) off the French company’s stock market value, as analysts said it now looked almost impossible for the firm to hit its 2020 targets.

Publicis said late on Wednesday its organic revenue - which excludes acquisitions, divestments and currency moves - fell 0.3 percent in the last quarter of 2018 to about 2.49 billion euros, far below analysts’ average forecast for growth of 2.5 percent.

The decline was led by a drop in ad spending by major “fast-moving consumer goods”, or FMCG, companies such as Procter & Gamble and Unilever.

FMCGs account for 25 percent of Publicis’ revenue and are particularly important in its biggest market, the United States, but are increasingly switching to digital marketing or even bringing the production of commercials in-house.

Publicis boss Arthur Sadoun, who succeeded company veteran and current chairman Maurice Levy in 2017, has promised to offset the decline in ad spending by steering the business closer to consulting groups by offering clients technological tools on top of traditional creative marketing campaigns.

That helped it to win key media budgets for GlaxoSmithKline and Fiat-Chrysler late last year.

But the weakness of the fourth-quarter figures sent a shockwave through the sector, with shares in U.S. rivals Omnicom and Interpublic dropping during New York trading on Wednesday, and Britain’s WPP sliding on Thursday.

“The scale of the miss in the fourth quarter took us by surprise, with attrition among existing accounts negating new business gains,” Deutsche Bank said in a note to clients.

“What’s more, it appears that the trend is due to continue into the first quarter of 2019.”

On a two-hour call with analysts, Sadoun said he expected an improvement in organic growth in the second quarter of 2019 and stuck with his 2020 target of 4 percent growth.

But some analysts remain to be convinced.

“(The 2020 target) looks mathematically near-impossible at this stage given current trends,” said Kepler Cheuvreux’s Conor O’Shea.

At 1300 GMT, Publicis shares were down 14.6 percent at 46.99 euros, the second-biggest fall by a European blue-chip stock. They earlier touched a six year-low of 46.93 euros

$1 = 0.8819 euros Additional reporting by Derek Francis and Martinne Geller; Editing by Alexander Smith and Mark Potter