I am looking for a quote from Max Clifford along the lines of " I have
had the ability to lie since I was a child". Looking for source and
exact quote.

Only came across this one ...

The Republic's quotable quotes
http://www.1rev.net/archive/33-repub/repub_33_make.html

"Most of what you read in the papers is lies. I should know because a
lot of the lies are mine."
-- Max Clifford

When Clifford was a child:

I was a "disruptive influence" at school. I was not remotely academic
and spent as little time as possible in the classroom. I was good at
sport so I often escaped lessons because I'd be off representing the
school at cricket, football, swimming and so on. When I was in class I
would grasp the basics in the first five minutes and then my
concentration would drift away and I'd spend the rest of the time
mucking about. I was easily bored. I often got sent out. The
headmaster would see me standing outside the classroom door and say,
"Oh, it's you again, Clifford."

from: My Best Teacher, by  Pamela Coleman 
Times Educational Supplement  12 July 2002
http://www.tes.co.uk

"I was always instinctively good at lying"
 
Max Clifford [LBCs Publicity Agent], as quoted in a new book of interviews.
 
Sunday Times 17th November 2002.