Theresa May said that Britain should be a country that works for everyone and opportunity is "fairly shared".
"Government cannot stand aside when it sees social injustice and unfairness," she said.
I want us to be a country where it doesn't matter where you were born, who your parents are, where you went to school, what your accent sounds like, what God you worship, whether you are a man or a woman, gay or straight, black or white.
All that should matter is the talent you have and how hard you're prepared to work.
Theresa May has said that a decision on where to build extra airport capacity in the southeast of England will be made soon.
Speaking at the Conservative Party Conference in Birmingham, the prime minister said: "We will shortly announce a decision on expanding Britain's airport capacity."
Heathrow and Gatwick have been competing for approval to build an extra runway.
Mrs May is expected to make an announcement on the repeatedly delayed decision in October, after it was pushed back again following June's EU referendum.
Theresa May will "always fight" to preserve the unity of the United Kingdom.
The Prime Minister said the reputations of many UK institutions echoed throughout the globe.
"All possible because we are one, united kingdom: England, Scotland, Wales and Northern Ireland", she said.
"And I will always fight to preserve our proud, historic union and will never let divisive nationalists drive us apart".
Labour is the new "nasty party", Theresa May told the Conservative Party Conference.
The Prime Minister used her speech to condemn Jeremy Corbyn's "divisive" Labour.
She told activists in Birmingham that she would "put the power of government squarely at the service of ordinary working-class people".
May said: "Only we can do it. Because the main lesson I take from their conference last week is that the Labour Party is not just divided, but divisive".
She added: "That's what Labour stands for today. Fighting among themselves. Abusing their own MPs. Threatening to end their careers. Tolerating anti-Semitism and supporting voices of hate.
"You know what some people call them? The nasty party".
Theresa May said she values the "spirit of citizenship" and urged businesses to respect the UK's "social contract".
The Prime Minister said she wanted businesses and employers in Britain to thrive, but urged them to "commit" to the wider population.
"We also value something else: the spirit of citizenship", she said.
"That spirit that means recognising the social contract that says you train up local young people before you take on cheap labour from overseas.
"That spirit that means that you do as others do and pay your fair share of tax".
Prime Minister Theresa May said she wants to set the Conservative Party on to the "new centre ground of politics".
Speaking at the Conservative conference in Birmingham, she said the party would be "built on the values of fairness and opportunity where everyone plays by the same rules."
Britain's vote to leave the European Union was spurred by a sense that the world "works for a privileged few".
Theresa May told the Conservative Party Conference that the vote had a broader meaning that just severing ties with the bloc.
"For the referendum was not just a vote to withdraw from the EU - it was about something broader, something the EU had come to represent", the Prime Minister said.
"It was about a sense - deep, profound and, let's face it, often justified - that many people have today, that the world works well for a privileged few but not for them.
"It was a vote not just to change Britain's relationship with the EU, but to call for a change in the way our country works and for the people for whom it works".
A "quiet revolution" set in motion Britain's departure from the European Union, Theresa May said.
The Prime Minister, addressing the Conservative Party Conference in Birmingham, described Brexit as a "once-in-a-generation chance to change the direction of our nation for good".
May told the conference that the vote to leave the EU on June 23 meant that change is inevitable.
"Change has got to come too because of the quiet revolution that took place in our country", she said.
"A revolution in which millions of our fellow citizens stood up and said they were not prepared to be ignored any more".
She added: "This is a turning point for our country, a once-in-a-generation chance to change the direction of our nation for good.
"To step back and ask ourselves what kind of country we want to be".
Prime Minister Theresa May joked about the Foreign Secretary's ability to stay "on message" at the opening of her speech on the last day of the Conservative party conference.
"When we came to Birmingham this week, some big questions were hanging in the air," May said.
"Can Boris Johnson stay on message for a full four days? Just about," she added.
Her quip was met with laughter and applause by delegates including Boris Johnson himself.