Labour will campaign for a "real social Europe" that has greater public ownership and stronger workers' rights, Jeremy Corbyn will tell supporters.
The party wants the UK to remain part of the European Union because it brings jobs and investment as well as protections for employees, but it wants "progressive change" in the 28-member bloc, the opposition leaders will say.
Reforms secured by Prime Minister David Cameron that curb benefit payments for low-paid migrants "won't put a penny in the pockets" of British workers or stop their wages being undercut, Labour members will be told.
Mr Corbyn, a long-standing critic of the EU, was earlier this week forced to defend his campaigning role after criticism from backbenchers that the vote could be "lost" unless the party made a more "passionate" case.
He will tell the Labour North conference in Newcastle: "We will be campaigning to keep Britain in Europe in the coming referendum because it brings investment, jobs and protection for British workers and consumers.
"But we will also be campaigning with our allies for reform and progressive change in Europe: for more democracy, jobs and sustainable growth, public ownership and workers' rights - in other words, a real social Europe.
"The North East is the only part of Britain that still has a trade surplus and over half your region's exports go to Europe. The good jobs and quality apprenticeships here in the North East make the case for staying in Europe.
"Let us be clear too, taking benefits off low paid migrants won't put a penny in the pockets of workers in Britain or stop the undercutting of UK wages through the exploitation of migrant workers."
Ahead of next week's budget, the Labour leader will insist that Conservative austerity measures are a "political choice not an economic necessity".
"Their cuts are both brutal and unnecessary," he will say.
"In 2010 they said that their 'long-term economic' plan would sort all this out, that the deficit would be eradicated by now.
"Their long-term plan has turned out far longer than they imagined, but subject to short-term revision when it fails again and again. It is a blueprint in deepest Tory blue to shrink the state, to shrink people's security, stability and opportunity."
Mr Corbyn will also dismiss Chancellor George Osborne's so-called Northern Powerhouse policy as "southern hot air".
"The Government's own figures show Osborne talks the talk, but he doesn't walk the walk. When it comes to the Northern Powerhouse, Osborne's just not delivering," he will say.
"Look closely at the Government's infrastructure 'pipeline' – and you find that only a fifth is actually in construction and most of the investment for those projects is going to London and the South East."