A method and apparatus for interleaving an input data stream for parsed parallel concatenated code encoding, the method comprising the steps of: parsing the input data stream into a plurality of parsed data substreams; and forming sets of shared information bits, wherein each of the sets of shared information bits comprises information bits in common with respective pairs of the plurality of parsed data substreams. In a variation, a further step comprises constructing constituent permutations of one or more of the sets of shared information bits. In yet a further variation, a further step comprises interlacing respective pairs of the sets of shared information bits to form respective interleaved data substreams.