Iain Duncan Smith has said that his two years in charge of the Conservative Party profoundly changed his outlook on life.

The comments came as the outgoing party leader delivered a lecture to the Centre for Policy Studies on Thursday evening, ironically entitled "The first Conservative government of the 21st Century".

The speech had been scheduled for some time and was meant to highlight the policies set out at this autumn's party conference, but Duncan Smith admitted with good humour that it had been "somewhat overtaken" by events.

Despite being ousted as party leader following a no confidence vote by his MPs, Duncan Smith indicated that he was determined to continue giving his backing to the policies that were developed under his leadership.

He said the polices were based on four inter-linked principles "which will be my legacy to this party".

"The first is the need for a complete renewal of our public services," he said.

"The second is the need to place social justice, and concern for the plight of the vulnerable, at the very core of Conservative thinking.

"The third is the need for freedom, the rule of law and a strong and competitive economy.

"And the fourth is the need to defend the state itself, and the constitutional arrangements of the United Kingdom."

Duncan Smith told his audience that "although I will not lead the first Conservative government of this century, I believe I have provided its manifesto, its policy prospectus".

The departing leader described his time in charge as "an immense honour" and called for a quick decision on who would replace him.

"The new leader will have my absolute loyalty," he said.

"And I encourage all those members of the voluntary party who made me the first leader of the party elected by the grass roots, to also give that leader their whole-hearted support."

He also warned his party's fractious MPs that they must "never again allow...private interests and squabbles to distract us from the task of opposition".

Duncan Smith singled out his party's renewed focus on social issues as one of the highlights of his time as party leader.

"My social justice agenda springs from my visit to Easterhouse in February 2002," he said.

"That was dismissed by many as a media stunt.

"But that visit - and many more to hard-pressed neighbourhoods since - have had a profound impact on me.

"If my main legacy to the Conservative Party is a body of policy, my commitment to fight poverty is that body's beating heart."

And he said that over the coming weeks he would "think carefully about how I, personally, will take that commitment forward".

"I am personally determined that a hard-headed and open-hearted approach to questions of poverty becomes a central theme of conversation and debate within the Conservative Party," he added.

With the burdens of leadership lifted from his shoulders, Duncan Smith revealed the personal journey that he has experienced as leader of the Conservatives.

"A great deal has changed for me over the past two years," he said.

"Serving as leader of the opposition meant challenges on a scale that no one who hasn't done the job can appreciate.

"There have been some privileges - but many more problems. All of this - from the sweet moments of victory to the bitter moments of defeat - have changed me."

He said that "anyone with a modicum of sensitivity and insight" would have been changed by the "appalling" scenes of deprivation in some parts of Britain.

"On this journey, I've been reminded of something that lies deep in the Conservative conscience, buried too deep for too long, that our party fulfils its greatest purpose when we bring social solidarity by delivering social justice."

He said that meeting with people fighting to help the poorest members of their community had "taught me more about leadership than any politician could have".

"The only meaningful freedoms for them are the freedom from fear and want, crime and addiction - they yearn not for license, but for order," said Duncan Smith.

"My journey is not a trip to an uncertain future - but the journey home.

"To a Conservative home, where the security of family and community bring hope and fairness.

"My journey is not over, my mission will continue. It is the Conservative mission for fairness, true to our inheritance, vital for our people, worthy of our nation."