  We present broad-band V and I imaging and long-slit spectroscopy in the
optical range 3600-7500A of the dwarf irregular galaxy HS 1442+4250. The oxygen
abundance 12+log(O/H)=7.63+/-0.02 (Z=Zsun/19) in the brightest H II region of
HS 1442+4250 places the galaxy among the most metal-deficient emission-line
galaxies. The low metallicity and blue colour (V-I)~0.4 mag of the
low-surface-brightness (LSB) component make HS 1442+4250 a likely rare young
dwarf galaxy candidate. We use four methods to estimate the stellar population
age in the LSB component of HS 1442+4250. Different star formation histories
are considered. The equivalent widths of hydrogen Halpha and Hbeta emission
lines, and of hydrogen Hgamma and Hdelta absorption lines, the spectral energy
distribution and the observed (V-I) colours of the LSB regions are reproduced
quite well by models with only young and intermediate-age stellar populations.
By contrast, the observational data cannot be reproduced by a stellar
population formed continuously with a constant star formation rate in the age
range from 0 to > 2 Gyr. While a faint old stellar population in HS 1442+4250
with an age > 2 Gyr is not excluded, we find no evidence for such a population
from the present data.
