1. A method for deghosting seismic data recorded from marine streamers with irregular receiver positions, comprising: obtaining seismic data for a seismic source activation and for a frequency after being transformed to a spectral domain; applying an iterative conjugate gradient scheme, using a preconditioner constructed according to a physical problem of deghosting seismic data from marine streamers, to the transformed seismic data, to provide a least squares solution to a normal set of equations for a deghosting system of equations; and inverse-transforming the solution back to a space-time domain to provide deghosted seismic data.