Montferrand completed the double over Swansea with a 24-19 win at St Helens.
But it was not all plain sailing for the French side as Swansea launched a brave attempt to pull the game out of the fire with a storming late rally.
Centre Steve Winn managed to touch down in a scramble in the 76th minute after the Swansea pack had led an assault on the visitors line.
Outside half Arwel Thomas slotted over the conversion but Montferrand managed to hold on and deservedly so.
The defeat left Swansea at the bottom of Heineken Pool Five with the Round 3 26-19 win over Bristol Shoguns their only triumph.
The home side got off to the worst possible start. Montferrand had scored two tries within eight minutes, winger Jimmy Marlu and centre Johnny Ngaumo the scorers.
French international outside half Gerald Merceron was named man-of-the-match, added one conversion and proceeding to notch four penalty goals.
Thomas, who has been sharing the No.10 shirt with Gavin Hanson all season, justified his inclusion as his three penalty goals kept Swansea in the game.
Swansea trailed 12-9 at the half, but any thoughts they may have had of a comeback were dashed as Merceron pinned back the All Whites back with an expert display of tactical kicking.
And his second half penalty goals hurt Swansea as the visitors extended their advantage.
Swansea fielded seven substitutes in the final minutes in a bid to find a winning formula, but their final effort was too little too late.