1. A method for deghosting seismic data recorded from marine streamers with irregular receiver positions, comprising: obtaining seismic data for each seismic source activation and for each frequency after being transformed to a spectral domain; applying an iterative conjugate gradient scheme, using a physically-based preconditioner, 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.