While I think the purported statement is GREAT, it was not in fact the speech given. Also, it was circulated around at least 3 years ago - not that it wouldn't be relevant today.

Here's Some comments from "HoaxSlayer" if you even believe that what HoaxSlayer puts out on the Web:

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Prime Minister Howard - Muslims Out Of Australia

Summary:
Email forward claims that former Australian Prime Minister John Howard told the media that immigrants should adapt to Australian culture, language and beliefs or leave the country. It also claims that Howard told Muslims who want to live under Islamic Sharia law that they should get out of Australia (Full commentary below).

Status:
Contains elements of truth, but is highly misleading and inaccurate

Update: 2009
In early 2009, an altered version of the message falsely claimed that it was then Australia's Prime Minister, Kevin Rudd who made the comments.

Update: 2011
In late 2010, yet another version of the message began circulating that claimed that it was the current Australian Prime Minister Julia Gillard who made the comments. Like the 2009 Kevin Rudd version, this claim has no basis in fact whatsoever.

Example:(Submitted, July 2008)
Subject: FW: Please read this! I know you will love it!

Canada & America Need A Leader Like This!

Prime Minister John Howard - Australia

Muslims who want to live under Islamic Sharia law were told on Wednesday to get out of Australia , as the government targeted radicals in a bid to head off potential terror attacks.

Separately, Howard angered some Australian Muslims on Wednesday by saying he supported spy agencies monitoring the nation's mosques. Quote: 'IMMIGRANTS, NOT AUSTRALIANS, MUST ADAPT. Take It Or Leave It. I am tired of this nation worrying about whether we are offending some individual or their culture. Since the terrorist attacks on Bali , we have experienced a surge in patriotism by the majority of Australians.'

'This culture has been developed over two centuries of struggles, trials and victories by millions of men and women who have sought freedom'

'We speak mainly ENGLISH, not Spanish, Lebanese, Arabic, Chinese, Japanese, Russian, or any other language. Therefore, if you wish to become part of our society . Learn the language!'

'Most Australians believe in God. This is not some Christian, right wing, political push, but a fact, because Christian men and women, on Christian principles, founded this nation, and this is clearly documented. It is certainly appropriate to display it on the walls of our schools. If God offends you, then I suggest you consider another part of the world as your new home, because God is part of our culture.'

'We will accept your beliefs, and will not question why. All we ask is that you accept ours, and live in harmony and peaceful enjoyment with us.'

'This is OUR COUNTRY, OUR LAND, and OUR LIFESTYLE, and we will allow you every opportunity to enjoy all this. But once you are done complaining, whining, and griping about Our Flag, Our Pledge, Our Christian beliefs, or Our Way of Life, I highly encourage you take advantage of one other great Australian freedom,