HTML accented characters (mostly french)

Good afternoon,
 
I've been debating left and right on the issue of HTML accented characters and if the equivalent ASCII code should be used to replace the actual accented characters or not -- most especially french accented characters (such as é, è, ê, etc...). 
 
I've had different opinions from various people, on using them or not and I need a concrete answer on the accessibility standpoint -- which is why I have contacted you. 
 
I tried finding the golden answer via your very large site, but could not pinpoint any specific details on the issue. Could you please enlighten my query so I can finally know which proper method to use. Please feel free to insert as many comments or details as you wish -- I really need a final answer to this great dilemma.
 
Thank you. Greatly appreciated.

Mark Bélanger 
Infographiste / Multimedia Designer 
Service d'infolangagerie / Technolinguistic Services 
Bureau de la traduction / Translation Bureau 
(819) 994-2243 | télécopieur / facsimile (819) 953-6432 
Mark.Belanger@tpsgc.gc.ca / Mark.Belanger@pwgsc.gc.ca 
975 boul. St-Joseph, Gatineau (Québec)  K1A 0S5 
975 St-Joseph Boulevard, Gatineau, Québec  K1A 0S5 
Travaux Publics et Services gouvernementaux Canada / Public Works and Government Services Canada 
Gouvernement du Canada / Government of Canada