The Ashes had gone into the match sitting top, one point ahead of Crediton, but the home side snatched the title with a hard-fought win.
Both teams scored two tries, with Tom Ronchetti and Dev Hosegood going over for the home side and Ryan Rayner and Ollie Mulberry for Saltash. But the difference was 13 points from the boot of Crediton’s Ollie Avery-Wright.
Both teams have secured promotion and should be competitive in Western Counties West.
Elsewhere in the division, OPMs’ disappointing season ended on a low, losing 64-19 at Hayle, while Liskeard-Looe did not fulfil their fixture at Honiton.
Tamar Saracens had to settle for runners-up spot in Devon Two, despite beating Salcombe 19-6 away, as rivals North Tawton hammered Dartmouth 61-12.
Devon Two’s bottom two sides DHSOB and Plympton Victoria both suffered last day defeats. DHSOB went down 45-0 at home to Illfracombe, while Plym Vic lost 54-3 away at Buckfastleigh.
Plymstock Albion Oaks secured runners-up spot in Devon One by trouncing third-placed St Columba & Torpoint 69-0. Saints were the only team that could have stopped them reaching the play-offs.
Title-winners Plymouth Argaum ended their league season on a high, beating Topsham 35-19 away, with tries from Jake Tufrey, Ellery Jones, Dave Hall, Jamie Burton and the ever-dangerous Dan James. Their attentions will now turn to the Lockie Cup final.
South West One West runners-up Ivybridge will go into their promotion play-off match on the back of a 34-29 away win at Clevedon.
They will battle it out with South West East side Towcestrians for a place in National League Three South West. Towcestrians lost 41-17 at Devizes.
Devonport Services secured sixth spot in Western Counties West with a 52-0 victory over bottom side St Ives at the Rectory. Tim Wheal (2), Andy Pond, Matt Gregory, Ty Busfield, Alex Percival and Fin Golding scored their tries.
Meanwhile, already relegated Tavistock put up a great fight against champions Teignmouth before losing 41-31.