Iain Duncan Smith has vowed never to walk away from the challenge of helping the most vulnerable members of society.

Continuing to place his campaigning emphasis on helping Britain's poorest people, the Conservative leader made a clear break from Margaret Thatcher's "much misrepresented quotation" that there is "no such thing as society".

"There is such a thing as society and Conservatives will nurture, protect and champion it," he pledged.

Duncan Smith was speaking at the launch of a new book which he said provided "further confirmation that my focus on helping vulnerable people is the central mission for twenty-first century Conservatives".

Admitting that the Conservative Party faced a challenge to "occupy territory that has not always been associated with us", the Conservative leader brushed off critics of his strategy.

He argued that helping vulnerable people "should not be a bolt-on extra to Conservatism but a defining part of who we are".

Developing his critique of the problems faced by areas such as Glasgow's Easterhouse estate, he argued that government had "squeezed out" alternative sources of security and opportunity.

"The state has undermined the professional independence of teachers, doctors and police officers by overloading them with bureaucracy," he said.

"The state has squeezed out independent community groups by only giving support to charitable groups who do as they are told."

"The state has offered a necessary helping hand to damaged families but it has been indifferent to whether other healthy relationships survive."

But he added that the problems should not be used as "an excuse to run away from the problems of Britain's most disadvantaged communities".

"I will never walk away from my mission to extend opportunity and security to everyone. We must tackle failing schools, crime, sub-standard healthcare, child poverty and insecurity in old age," said Duncan Smith.

Rather than seeking a bigger role for the state, the Conservative leader argued that the alternative was "a stronger society" - not the "lonely individualism" critics sometimes suggest his party favours.

"Government should be focused on strengthening the natural institutions of society - and not replacing or undermining them," he said.

Duncan Smith also called for a "new politics" that would be worthy of the idealism of the public.

"It offers the possibility of repairing the relationship between an unimaginative political system and a disillusioned electorate," he said.