The foreign secretary, Jack Straw, is attempting to block a new law that would punish negligent employers with heavy fines or imprisonment in cases of deaths or injury at work.

The Guardian has obtained details of a letter sent by Mr Straw 10 days ago to John Prescott, deputy prime minister and chair of the domestic affairs cabinet committee. In it, the foreign secretary casts doubt on the need to create a new crime of corporate manslaughter.