  We present a measurement of the volumetric rate of superluminous supernovae
(SLSNe) at z~1, measured using archival data from the first four years of the
Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). We develop a
method for the photometric classification of SLSNe to construct our sample. Our
sample includes two previously spectroscopically-identified objects, and a
further new candidate selected using our classification technique. We use the
point-source recovery efficiencies from Perrett et.al. (2010) and a Monte Carlo
approach to calculate the rate based on our SLSN sample. We find that the three
identified SLSNe from SNLS give a rate of 91 (+76/-36) SNe/Yr/Gpc^3 at a
volume-weighted redshift of z=1.13. This is equivalent to 2.2 (+1.8/-0.9)
x10^-4 of the volumetric core collapse supernova rate at the same redshift.
When combined with other rate measurements from the literature, we show that
the rate of SLSNe increases with redshift in a manner consistent with that of
the cosmic star formation history. We also estimate the rate of ultra-long
gamma ray bursts (ULGRBs) based on the events discovered by the Swift
satellite, and show that it is comparable to the rate of SLSNe, providing
further evidence of a possible connection between these two classes of events.
We also examine the host galaxies of the SLSNe discovered in SNLS, and find
them to be consistent with the stellar-mass distribution of other published
samples of SLSNe.
