I couldn't find if it really comes from a 1955 interview or not, but Camus wrote such a claim in his Preface to The Stranger (January 1955), available here in English translation (emphasis mine):
One would therefore not be much mistaken to read The Stranger as the story of a man who, without any heroics, agrees to die for the truth. I also happen to say, again paradoxically, that I had tried to draw in my character the only Christ we deserve. It will be understood, after my explanations, that I said this with no blasphemous intent, and only with the slightly ironic affection an artist has the right to feel for the characters he has created.
The same claim is repeated in his Théâtre Récits Nouvelles (1962), for which I found the original French version of the sentence:
Il m'est arrivé de dire aussi, et toujours paradoxalement, que j'avais essayé de figurer dans mon personnage le seul Christ que nous méritions.
Translated by me and Google Translate (I'm not sure if the tenses can be correct in the above translation of the 1955 version):
I also happened to say, and always paradoxically, that I had tried to represent in my character the only Christ that we deserved.
I couldn't find the exact quote "Meursault est le seul Christ que nous méritions" in any Camus writings, and very few results for this exact phrase even on the web. This suggests to me that it's a paraphrase of Camus's exact words, written with "Meursault est" so as to make the context clear, and then has been reproduced and quoted in this form.