The Monster Employment Index for Europe fell in January at the sharpest rate since the monthly survey began more than three years ago.
Monster's European Index - based on research of employers' job postings on more than 1,400 web sites in Germany, France, Britain, the Netherlands and Sweden - fell to 139 in January from 155 in December.
Monster said that was the biggest fall since December 2004. Roughly half of it was due to a seasonal slowdown, but it was too soon to tell whether fears of a global slowdown were driving the decline.
The Swedish index posted one of the heaviest falls, dropping to 187 from 204, while the British index fell to 160 from 174.
Each sector saw a fall in its index, with health care and social work job postings falling sharply, though historical data suggested that drop was largely seasonal in nature.
Education, training and library postings also fell, as did those in real estate, which slid for a third consecutive month to its lowest level in more than two years.
The index for banking, finance and insurance fell to 106 from 119.