Throughout his career, he rejected offers made to him by foreign laboratories and other parties. After returning to Morocco, Idrissi gained an interest in politics and was an ardent trade unionist and adopted Third-Worldism. He became a community activist and a politician under the banner of the Socialist Union of Popular Forces.
He became a professor at the Mohammadia School of Engineering and moved to Safi, where he conducted research in a number of laboratories in the late 1960s. Idrissis field of research focused on the recovery of uranium from phosphates, which was Moroccos biggest export. During his research, he mapped the Ganntour basin and its uranium repartition.
In 1968, he discovered a significant amount of uranium in Moroccan phosphates, which he announced to local press. Idrissi had estimated that about 72 thousand tons of uranium could be extracted annually as a low-cost byproduct from Moroccan phosphates. The media praised his discovery, and he supplied data regarding his findings to the IAEA.