Most Revd Justin Welby also said that Christians can be the most intolerant of all the different faith groups in the UK, despite Britain calling itself an inclusive society.
He made the comments in a speech to the Deputies of British Jews at their annual dinner last week.
In the speech he also apologised for the accusations made by Revd Stephen Sizer, a vicar in Surrey who said Israel was complicit in the September 11th terorrist attacks, prior to Holocaust Memorial Day.
Revd Sizer subsequently apologised and the Church of England banned him from publicly commenting on issues relating to the Middle East again.
Mr Welby told guests: "The worst poison pen letters I get are from other Christian groups on the whole.
"The reality is that we do not as faith groups in our society always exhibit the that secure tolerance to the world around us.
"Christians are as bad as anyone at this - in fact, if I dare to be competitive, I think we're worse."
The Archbishop also said that in order to tackle extremism, faith groups must stop issuing "bland", "anaemic" statements about what they have in common, and acknowledge their differences respectfully.
He said: "... we have to have the difficult conversations in safe spaces - and that's a very, very difficult thing to do.
"Can we model confidentiality, transparency and genuine respect for one another?
"We need to move to beyond inter-religious interaction in which we the usual suspects issue bland statements of anaemic intent... all desperate to agree with one another, so that the very worst outcome could possibly be that we end up acknowledging our differences.
"That is not enough in the face of the dangers we face at this time.
"It is disingenuous and ultimately dishonest, because alongside all that we hold in common and all that we share, there are profound differences too in what we believe and in the outworking of our faith."