Smith, who was due to meet Liam Williams for the interim WBO title and a possible world title shot, came in one pound 15oz over and is no longer eligible for the strap.
‘Beefy’ was given the option of attempting to drop the excess weight in two hours, but chose not to and therefore has forfeited the title.
Trainer Joe Gallagher looked bemused at what the scales were telling his fighter, who looked in superb condition despite coming in over.
The fight against Williams, set for Manchester Arena on Saturday night, still goes ahead as planned with only the Welshman able to claim the honour.
With a lucrative bout against Miguel Cotto in the pipeline, the question may now be asked as to whether Smith and the Puerto Rican would potentially be willing to meet above the super-welterweight limit.
A move up to middleweight also seems to be on the cards for Smith though, which would also bring a massive fight with Gennady Golovkin into play for 2018.
A high rating with the WBO means an encounter with stablemate Billy Joe Saunders could possibly happen in the future should Smith see his future above the limit he has now failed to make.