"Can I help you?" by shop clerks...impolite?

Is it considered bad for shop clerks to say to their customers "Can I help you?" instead of "May I help you?"?

"Can I help you" can be polite, but "May I help you" would usually be more polite.
Of course, either one can be rude if uttered with a nasty tone.

to most people, they mean the same thing. Perhaps since it's the grammatically correct form, "may I" is considered more polite. As JimmySeal said, in this case inflection is more important than word choice.

"Can I help you...?"
The implication is that of ability. 'Do you think I am able to help you?', or 'Do think you able to do it?'
It is a common greeting in shops, and it irks me. Sales clerks repeat this phrase day in, day out, and it can be delivered or replied to in an insulting manner.

"May I help you...?" Permission is being sought by the assistant. A service is being offered. The customer can decline or accept the invitation. 'May I...' is not loaded with the clerks or customers abilities. Saying it or replying to it with insolence doesnt work very well.

May I is a benign introduction, and the focus is on the service.

(edit)Upon reflection I should print this post on wee buisness cards to educate shop assistants everywhere who still use Can I...
Actually I am going to quit my job tommorrow and start on this right away. First thing tommorrow I am going to spend my savings on printer ink and cartridge paper.
Wow... Hollywood here I come! This is definitely a great script for a movie.
I'll travel the land sleeping rough... a couple of groupies following me... like Tom Hanks in Forrest Gump...and when I get home after 6 years on the road, the wife will greet me at the front gate without recognising me and say..."May I help you?"

Ultraman said:

"Can I help you...?"
The implication is that of ability. 'Do you think I am able to help you?', or 'Do think you able to do it?'
It is a common greeting in shops, and it irks me. Sales clerks repeat this phrase day in, day out, and it can be delivered or replied to in an insulting manner.
"May I help you...?" Permission is being sought by the assistant. A service is being offered. The customer can decline or accept the invitation. 'May I...' is not loaded with the clerks or customers abilities. Saying it or replying to it with insolence doesnt work very well.
May I is a benign introduction, and the focus is on the service.

Click to expand...

Can't say it any better...so I'll just quote it for all to read again! Excellent reply!

can i help you is generally ruder and less polite slightly. But if you use "may" you have to say "how may i help you"

Ultraman said:

"Can I help you...?"
The implication is that of ability. 'Do you think I am able to help you?', or 'Do think you able to do it?'
It is a common greeting in shops, and it irks me. Sales clerks repeat this phrase day in, day out, and it can be delivered or replied to in an insulting manner.
"May I help you...?" Permission is being sought by the assistant. A service is being offered. The customer can decline or accept the invitation. 'May I...' is not loaded with the clerks or customers abilities. Saying it or replying to it with insolence doesnt work very well.
May I is a benign introduction, and the focus is on the service.

Click to expand...

And at what point, not being blinded by prescriptivists or traditionalists, does the language change in favor of universally recognized common mans speech ? Can is used more frequently by nearly everyone to express permission. It has absolutely no relation whatsoever to shops or sales greetings in particular.

I think people more commonly say "can I help you?" rather than "may I help you?" as a 'greeting' in shops, but they both mean the same thing. Personally, I don't really notice the difference, it just doesn't register with me as the intent is the same. Sometimes it is annoying for the clerk to say this (whichever), sometimes not, it depends on the circumstances. If I'm going to get irritated by it I'll be irritated regardless of which turn of phrase they used; if not, not.

Elizabeth said:

And at what point, not being blinded by prescriptivists or traditionalists, does the language change in favor of universally recognized common mans speech ? Can is used more frequently by nearly everyone to express permission. It has absolutely no relation whatsoever to shops or sales greetings in particular.

Click to expand...

But as was mentioned: Can implies the ability to do something "Can I help you?" I'm sure you are physically able to yes. It is more common now days to hear this said instead of "may" but that does not make it correct.

"May I help you?" is asking permission to do it.

As one of our beloved (?!!) modal verbs, 'can' is used in many ways. One of them is to talk about ability. Another use is to ask for and give permission, and another to make requests and offers.

The use here is the offer, and Cambridge Advanced Online Dictionary (love it 'cause it's so quick and to the point!) defines 'can' in that sense as 'used in polite offers of help'.

'May' is perceived as somewhat more polite I'd suggest, and is becoming slightly old-fashioned, unfortunately. I find it gentler than 'can', less direct.
Most of all I like the one that's more and more common here when you're browsing in clothes shops (and others) - 'Are you OK/alright there? Rather than having to reply with the negative 'no' (you can't/may not help me) if you don't want assistance, the answer is 'yes' (i'm alright/OK thanks!)

Now, please don't get me started on supermarket etc experiences here in the UK near London, where you'll be lucky to get a thank you, and often feel like you're greatly putting the staff out by asking to buy something in the first place!!

Thanks for your help, guys!