The present invention relates to fire-retarded compositions comprising, by weight, the total being 100 parts: 50 to 75 parts of a blend of a polyamide (A) and a polyolefin (B), 25 to 50 parts of a blend comprising: 0.1 to 48.8 parts of a fire retardant, 0.1 to 30 parts of a phosphorus-containing plasticizer, 0.1 to 10 parts of a zeolite, the total of these three products being between 25 and 50. These compositions have a V0 or V1 classification according to the UL94-VB test when a fire test is carried out on test specimens 1.6 mm in thickness. They have many advantages, in particular the elongation at break measured according to ISO R 527-1B exceeds 100%. As regards the impact strength, they have a non-brittle behaviour in multiaxial impact at room temperature according to ISO 6603-2 (at a rate of 7.7 m/s). They retain at least 50% of their mechanical properties after ageing for seven days at 120° C. in hot air. These compositions are useful for insulating and protecting electrical cables and optical fibres and for moulding electrical cases and connectors.