I got married in March 2012. Moved to a new location and filed my taxes yesterday with tax consultant, as most of my colleagues were going there. He filed the status as "Married - Filing Jointly". When I checked with him if I should be married in 2011 to do that, he mentioned that is fine. I kept quiet thinking that he'd know as a tax consultant.

Later when I came home and googled, I saw that I should file as single. I started bugging him about it to make sure if nothing is filed wrong and he says it is fine as long as I am married before filing taxes. He says it is mentioned in IRS Publication 17 but I didn't find it anywhere. He says he couldn't point me to the exact page etc. Tried finding something related over the internet until now since I came from office by even skipping dinner and haven't found anything.

Now is he right about being allowed to file as married if I am married when filing taxes? Should I be filing amendment?

Your consultant is wrong. You must be legally married as of Decemberr 31, 2011 to file as Married on your 2011 tax return. I suggest that you run from this so-called "consultant" and find someone who knows what he's doing.

You are not married for 2011 tax return.
Yes, you must file amended tax return and properly done tax return as Single. Don't rush; wait till IRS processes your joint return.