Theresa May will tell the world's most powerful leaders they are not doing enough to tackle modern slavery as she warns it is the greatest human rights issue they are facing.
Radical action is needed to stamp out the "vile" crime but the international response has been fragmented, she will say at the G20 summit.
Tackling slavery has been one of Mrs May's key priorities since she was home secretary.
She will urge the G20 to work together to meet the United Nations' target of wiping out the crime by 2030.
Ahead of the discussions, Mrs May said: "This is the great human rights issue of our time.
"Tackling human trafficking and modern slavery remains a top priority for this government and we are committed to stamping out this abhorrent crime.
"In the UK we have set up the first ever government taskforce for modern slavery, bringing together every relevant department to co-ordinate and drive all our efforts in the battle against this cruel exploitation.
"But if we are to eradicate modern slavery around the world, we need to go much further.
"Victims will only find freedom if we cultivate a radically new, global and coordinated approach to defeat this vile crime.
"And that is why today at the G20 summit I am calling on the international community to follow Britain's lead in prioritising action in this area, in particular in supply chains."