In a defiant speech to the TUC conference, he insisted the Government's welfare reforms had cost lives and branded proposed restrictions on strikes an attack on civil liberties.
He also called for "solidarity" with workers around the world, blaming a "free market philosophy" for workplace tragedies in China.
The rallying call came after a tricky start to Mr Corbyn's stewardship of the party following his overwhelming election victory.
Many MPs, including frontbenchers, have signalled disquiet over the appointment of hardliner John McDonnell as shadow chancellor.
There are also complaints that none of the most senior jobs in his top team have gone to women.
The 20-minute quick-fire address to delegates in Brighton, delivered tieless, was originally intended to include a passage invoking Margaret Thatcher's 1980s phrase to warn that the Conservatives still regard unions as "the enemy within".
However, Mr Corbyn did not deliver the pre-briefed lines, with Labour officials saying he was working from notes and simply "forgot".
Mr Corbyn said the TUC conference was a "shared celebration of our values as a Labour and trade union movement".
"Values of solidarity, of compassion, of social justice, of fighting for the under-privileged, and for all working people at home and abroad. Those are the values that have shaped me and my political life," he said.
Opposition to welfare cuts
He signalled that Labour would now oppose all the Tories welfare changes, including the benefit cap.
"Labour will oppose the Welfare Bill in full. We oppose the benefit cap. We oppose social cleansing," he said.
"We will bring the welfare bill down by controlling rents and boosting wages, not by impoverishing families and socially cleansing our communities."
Angry retort to jibes
The new Labour leader delivered an angry retort to jibes that he is a "deficit denier".
"But then they spend billions cutting taxes for the richest families or for the most profitable businesses," he said.
"What they are is poverty deniers - ignoring the growing queues at food banks, ignoring the growing housing crisis, cutting tax credits when child poverty rose by half a million under the last government to over four million.
"Let's be clear - austerity is a political choice, not an economic necessity."