Theresa May will insist the state has a significant role to play in helping shape society as she sets out her vision to help people who are struggling to get by.
The Prime Minister will vow to tackle the "everyday injustices" faced by those who feel they have been ignored by Westminster as part of her "shared society" vision.
Mrs May has made helping those who are "just about managing" a key goal in her administration and she will promise a significant shift in the way government acts.
The speech in London on Monday, the first of a series of interventions on domestic policy over the coming weeks, is aimed at showing that Mrs May's term in office will not be defined by Brexit.
Her mission statement will mark a decisive break from Conservative predecessors Margaret Thatcher - who once declared that "there is no such thing" as society - and David Cameron, whose own Big Society agenda relied on voluntary organisations rather than state intervention.
Mrs May will use the speech in London to argue that previous administrations had focused too narrowly on the very poorest through the welfare system.
She will say that people just above the welfare threshold felt the system was "stacked against them".
Setting out her plans, Mrs May will say: "This means a government rooted not in the laissez-faire liberalism that leaves people to get by on their own, but rather in a new philosophy that means government stepping up - not just in the traditional way of providing a welfare state to support the most vulnerable, as vital as that will always be.
"But actually in going further to help those who have been ignored by government for too long because they don't fall into the income bracket that makes them qualify for welfare support.
"It means making a significant shift in the way that government works in Britain. Because government and politicians have for years talked the language of social justice - where we help the very poorest - and social mobility - where we help the brightest among the poor.
"But to deliver the change we need and build that shared society, we must move beyond this agenda and deliver real social reform across every layer of society so that those who feel that the system is stacked against them - those just above the threshold that attracts the government's focus today, yet those who are by no means rich or well off - are also given the help they need.
"Because people who are just managing, just getting by don't need a government that will get out of the way, they need a government that will make the system work for them. An active government that will work for them and allow them to share in the growing prosperity of post-Brexit Britain."
Mrs May's goal is to change the way the system works for those struggling to get by, facing challenges such as getting their children into good schools or climbing on to the housing ladder.
She will say: "While the obvious injustices receive a lot of attention - with the language of social justice and social mobility a staple of most politicians today - the everyday injustices are too often overlooked.
"If you're from an ordinary working class family, life is much harder than many people in Westminster realise.
"And at the same time, all too often in the past people have felt locked out of the political and social discourse in Britain."
Mrs May said her vision of a "shared society" was aimed at tackling "both the obvious and everyday injustices" in an effort to "overcome division and bring our country together".
She will say: "The shared society is one that doesn't just value our individual rights but focuses rather more on the responsibilities we have to one another. It's a society that respects the bonds that we share as a union of people and nations.
"The bonds of family, community, citizenship, strong institutions. And it's a society that recognises the obligations we have as citizens - obligations that make our society work."
Mrs May will appear on the new Sophy Ridge On Sunday show on Sky News to set out further details of her plan, which is expected to include a package of measures to people with mental health problems.