We have used force-free extrapolations of photospheric magnetic field observations from Marshall Space Fllght Center to compute the total intensity and circular polarisation of sunspot associated emission from active region 2502 in the period June 13 to 15, 1980. The computed maps were compared to high resolution observations of tne same active region obtained witn tne Westerbork Synthesis Radio Telescope, Tne most interesting aspect of tne active region was tne developement of a new spot between the proceeding and the following spots on June 14, wnich subsequently merged witn the preceeding spot. The new spot
was associated witn enhanced microwave emission with a peak brigtness temperature in excess of 4 10^6 K. Our model computations are In satisfactory agreement witn tne sunspot observations for June 13, nowever tbey falled to reproduce tne
enhanced emission associated witn tne new spot on June 14 and 15. We snow tnat unrealistic values of tne conductive flux are required for the interpretation of tne emission of the new sunspot in terms of thermal processes. We suggest tnat tnis source Is due to gyrosynchrotron radiation from mildly relativistic electrons accelerated by reslstive instabiltles in tne evolvlng magnetic field.