Abstract In 2003–2004 the NA48/2 Collaboration at CERN collected a large sample of K± decays. Using data taken with minimal trigger conditions, a sample of 2.5×106K±→π0μ±ν and 4.0×106K±→π0e±ν events was recorded, and allows precise measurements of the decay form factors. This report describes the event selection and the fitting procedure, and gives a preliminary result for the form factors in various parameterizations. In addition, with the full data sample collected, more than one million K±→π+π−e±ν and about 45000K±→π0π0e±ν decays has been analysed. An improved determination of the branching ratio and high precision form factor measurements for K±→π+π−e±ν, and a preliminary result for the branching ratio of K±→π0π0e±ν are presented in this paper. Future prospects include the observation of several thousands decays in similar muonic modes that will be studied at the NA62 experiment.