The results from the IFMOS ESA 1-5 microns integral field multiobject spectrograph study are presented. A review of the science requirements indicates that integral field 2D spectroscopy is a powerful concept of great value for the NGST. We present the opto-mechanical design of the instrument, based on image slicers. A low resolution and a high resolution channels are working in parallel, with only one mechanical motion. The low resolution channel covers a field 40 x 46 arcsec(2) at R similar...