Since this is an issue that is often talked about, I've looked at the number of Muslims among the immigrants in France. Religion is not asked in the French census, so I've looked at the countries of origin of the immigrants. For each country of origin, I have assigned the percentage of Muslims in that country as published by the Pew Research Center here:
http://features.pewforum.org/muslim-population/
Here are the results. In 2010, there were 5,405,754 immigrants living in Metropolitan France. 42.8% of them were potentially Muslim (using the percentages of the Pew Research Center), and 57.2% were non-Muslim. The increase in the total number of immigrants from Jan. 2008 to Jan. 2010 was due 46.3% to Muslim immigrants and 53.7% to non-Muslim immigrants. The percentage of potentially Muslim immigrants in Metropolitan France thus rose only very slightly from 42.7% of all immigrants in Jan. 2008 to 42.8% in Jan. 2010.
Regarding the immigrants from sub-Saharan Africa (black and purple areas on my map), 662,917 lived in Metropolitan France in Jan. 2010. 38.4% of them were potentially Muslim, and 61.6% were non-Muslim. The increase in the total number of sub-Saharan African immigrants from Jan. 2008 to Jan. 2010 was due 39.3% to Muslim immigrants and 60.7% to non-Muslim immigrants. The percentage of potentially Muslim immigrants among the sub-Saharan African immigrants in Metropolitan France thus rose only very slightly from 38.3% of all sub-Saharan African immigrants in Jan. 2008 to 38.4% in Jan. 2010.
The largest groups of Muslim immigrants living in Metropolitan France in 2010 came from:
- Algeria: 716,177 Muslim immigrants
- Morocco: 670,056
- Turkey: 242,244
- Tunisia: 241,152
- Senegal: 76,217
- Mali: 56,551
- Ivory Coast: 25,845
- Comoros: 25,109
- Egypt: 22,604
- Lebanon: 21,073 (probably an exaggerated number, because the Lebanese immigrants in France are more predominantly Christian that is the case in the general population of Lebanon)
- Guinea-Conakry: 19,854
- Iran: 19,371
- Pakistan: 18,204
- Mauritania: 14,067
- Cameroon: 12,341