There are provided a negative-working photosensitive composition which can
be cured by infrared rays and is less likely to suffer polymerization
inhibition by oxygen during radical polymerization, and also exhibits
high adhesion with a metal, and a negative-working photosensitive
lithographic printing plate which is capable of directly forming images
by irradiation with infrared rays from a solid or semiconductor laser
based on digital signals, and also has high sensitivity and excellent
printing durability. The negative-working photosensitive composition
contains an infrared absorber (A), an organoboron compound (B) which
functions as a polymerization initiator by using in combination with the
infrared absorber (A), a compound having a polymerizable unsaturated
group (C) and a diazo resin (D), and the negative-working photosensitive
lithographic printing plate comprises a support, and a photosensitive
layer containing the negative-working photosensitive composition formed
on the support.