The disc around PDS 70 hosts two directly imaged protoplanets in a gap.Previous VLT/SPHERE and recent James Webb Space Telescope/NIRCam observationshave hinted at the presence of a third compact source in the same gap at ~13au, interior to the orbit of PDS 70 b. We reduce seven published and oneunpublished VLT/SPHERE datasets in YJH and K bands, as well as an archivalVLT/NaCo dataset in L' band, and an archival VLT/SINFONI dataset in H+K band.We combine angular-, spectral- and reference star differential imaging tosearch for protoplanet candidates. We recover the compact source in all epochs,consistent with the JWST detection, moving on an arc that can be fit byKeplerian motion of a protoplanet which could be in a resonance with PDS 70 b &c. We find that the spectral slope is overall consistent with the unresolvedstar and inner disc emission at 0.95--1.65$\mu$m, which suggests a dustscattering dominated spectrum. An excess beyond 2.3$\mu$m could be thermalemission from either a protoplanet or heated circumplanetary dust, variability,or inner disc contamination, and requires confirmation. While we currentlycannot rule out a moving inner disc feature or a dust clump associated with anunseen planet, the data supports the hypothesis of a third protoplanet in thisremarkable system.