That is far above the threat level globally, reflecting the activity of fishing nations such as Spain, Portugal, France and Britain, the Swiss-based conservation group said.
The IUCN hopes that its findings will drive tougher fishing controls in the European Union -- and recommended a zero catch for spiny dogfish and all deepwater sharks, and an end to fishing for common skates.
"Action is absolutely necessary to change the current course toward extinction of these remarkable ocean animals," said Sonja Fordham, co-author of the first IUCN report assessing threat levels for sharks specifically in the northeast Atlantic.
The IUCN's Red List details the world's wildlife with the bleakest prospects -- threatened species grouped in descending order of risk as critically endangered, endangered, or vulnerable.
The next categories are "extinct in the wild" and "extinct."
Critically endangered sharks in the Northeast Atlantic included the gulper shark, prized in the cosmetics industry for its liver oil, and the two sharks most valued in Europe for their meat -- the spiny dogfish and porbeagle sharks.
The basking shark, the world's second largest fish, was listed as vulnerable.
Some 26 percent of sharks and rays in the Northeast Atlantic region were classified as threatened, compared to 18 percent for the same species globally, the report found.
"Deepwater sharks are faring worse in this region than globally, due to loosely regulated, targeted fishing by European vessels," it said.
Spiny dogfish and porbeagle are subject to EU fishing quotas, but the IUCN said these quotas were too generous.
"These species are among the few that are subject to EU fishing quotas and yet those limits are set well above the zero catches advised by scientists with the International Council for Exploration of the Sea (ICES) for avoiding collapse."
In mid-December in Brussels the European Council of Ministers will agree 2009 EU catch limits for skates and rays as well as spiny dogfish and porbeagle sharks.
The IUCN works with environmental groups and government agencies to compile environmental knowledge and prepare and implement national conservation and biodiversity strategies.
(Reporting by Gerard Wynn; Editing by Charles Dick)