  Searches for young gas giant planets at wide separations have so far focused
on techniques appropriate for compact (Jupiter sized) planets. Here we point
out that protoplanets born through Gravitational Instability (GI) may remain in
an initial pre-collapse phase for as long as the first $ 10^5-10^7$ years after
formation. These objects are hundreds of times larger than Jupiter and their
atmospheres are too cold ($T\sim$ tens of K) to emit in the NIR or H$\alpha$
via accretion shocks. However, it is possible that their dust emission can be
detected with ALMA, even around Class I and II protoplanetary discs. In this
paper we produce synthetic observations of these protoplanets. We find that
making a detection in a disc at 140 parsecs would require a few hundred minutes
of ALMA band 6 observation time. Protoplanets with masses of 3-5 $M_J$ have the
highest chance of being detected; less massive objects require unreasonably
long observation times (1000 minutes) while more massive ones collapse into
giant planets before $10^5$ years. We propose that high resolution surveys of
young ($10^5-10^6$ years), massive and face on discs offer the best chance for
observing protoplanets. Such a detection would help to place constraints on the
protoplanet mass spectrum, explain the turnover in the occurrence frequency of
gas giants with system metallicity and constrain the prevalence of GI as a
planet formation mechanism. Consistent lack of detection would be evidence
against GI as a common planet formation mechanism.

Earth and Planetary Astrophysics;Solar and Stellar Astrophysics