LONDON -(Dow Jones)- Shares in U.K. directories publisher Yell Group PLC (LSE:YELL) ( YELL.LN) slumped to an all-time low Friday after a U.S. peer lowered its own financial guidance amid a worsening economic outlook.

At 1014 GMT shares in Yell, the publisher of Yellow Pages in the U.K. and Yellow Book in the U.S., were trading down 8 pence, or 3.5% at 234 pence, leaving the company's market capitalization at GBP1.8 billion.

The company's stock has declined in value by more than 60% over the past year, prompted by downgrades to earnings forecasts as the outlook for both its U.K. and U.S. businesses has deteriorated.

U.S. directories publisher R.H. Donnelley Corp. (NYSE:RHD) (RHD) Thursday blamed a cut in advertising spend, a reduction in new business startups and a rise in advertisers unable to pay their bills for the cut in its guidance.

The weakness in Yell's shares Friday comes less than a month after its shares plummeted by over 15% after the company warned that its U.K. operation would miss fourth-quarter sales guidance amid a deteriorating economic environment.

Yell said Feb. 7 its U.K. fourth quarter sales would grow at roughly 2% compared with previous guidance of around 3%.

In April 2007 the company sharply lowered its U.S. organic revenue growth forecasts due to increasing competition from new entrants to the market.

UBS said Friday the worsening outlook from R.H. Donnelley (NYSE:RHD) "could bode ill for Yell, and noted that the company's debt position could come into renewed focus.

Citigroup said that a negative outlook statement "was always going to put pressure on Yell," but noted that R.H. Donnelley (NYSE:RHD) has a much greater exposure to national advertising expenditure, and has higher pricing.

Lehman Brothers noted that Yell got roughly half of its sales and 40% of underlying earnings from the U.S.

Yell was spun off BT Group PLC (NYSE:BT) (BT), the former U.K. telecoms monopoly in 2000, bought by private equity firms and later floated on the London Stock Exchange in 2001.

At the time of the early February downgrades, Numis Securities said the selloff reflected a "shock to the market," as the company had previously been presumed to be "recession resilient."

Company Web site: www.yell.com

-By Jessica Hodgson, Dow Jones Newswires; +44 207 842 92 93; jessica.hodgson@ dowjones.com

    (END) Dow Jones Newswires   02-29-08 0541   Copyright (c) 2008 Dow Jones & Company, Inc.