Thousands of Britain's biggest firms will be forced to reveal whether they have taken action to ensure they do not use child or slave labour under plans set out by the Prime Minister.
David Cameron made the commitment as he prepared to become the first British leader to visit Vietnam, a country which has been the source of criminal gangs ruthlessly exploiting child labour in the UK.
The Prime Minister will use his trip to offer extra co-operation with the Vietnamese authorities to combat human trafficking.
The announcements are part of a package aimed at the problem of "modern day slavery" where people, often victims of illegal people smugglers, are forced into servitude.
Under measures designed to ensure firms are accountable for their supply chains, all large companies will be required to publish an annual statement setting out what steps they are taking to ensure that slave labour is not being used.
The plan, which will apply to more than 12,000 firms with a turnover of £36 million or more from October, will expose companies which do not thoroughly check on their suppliers.
Mr Cameron said: "This measure is one of the first of its kind in the world and it will be a huge step forward, introducing greater accountability on business for the condition of their supply chains.”
On Friday a raft of new measures enshrined in the Modern Slavery Act will come in to force, including trafficking reparation orders which encourage the courts to use seized assets to compensate victims, and prevention orders to restrict the activities of potential slave masters.
Vietnam is one of the main source countries for victims of human trafficking in the UK and anti-slavery commissioner Kevin Hyland will lead a fact-finding mission to the south-east Asian nation later this year to look at what more can be done to work with the authorities there.
Extra assistance on offer will include funding for an additional shelter for survivors of trafficking, particularly women or children, help to prevent people falling into the grips of people smugglers in the first place and an information campaign in provinces of Vietnam where it is a particular concern.
Ahead of his visit to Hanoi, the Prime Minister said: "The scourge of modern slavery has no place in today’s society and I am proud of all that Britain is doing to wipe it out.
"Later this week, new measures will come in to force in the UK to provide greater protection and compensation for victims and to make sure that those responsible face tougher sanctions. But there is still much more to do.
“It is shocking that of thousands of Vietnamese children in the UK are being used for profit by criminal gangs and that dozens more children are estimated to arrive on our shores every month.
"That’s why it’s so important that we work with Vietnam to identify what more we can do to tackle this issue together.
"I’m delighted that the UK’s independent anti-slavery commissioner, Kevin Hyland, has agreed to visit Vietnam later this year to look at what practical support and training we can provide.
"And we will fund a second shelter for child victims of trafficking and returnees to ensure they get the care and support they need as they reintegrate."
Mr Hyland said the focus of his visit would be on "improved efforts to prevent these crimes from ever occurring in the first place" with work in the rural areas of Vietnam where many victims originate, as well as efforts to tackle the gangs already operating in the UK.
"Vietnamese criminal gangs operating across the UK are ruthlessly exploiting Vietnamese children in multiple ways to maximise the profit that can be gained from them," he said.
"This includes being exploited in forced labour in cannabis factories and nail bars, as well as an increasingly diverse range of exploitative activities, as the gangs move in to other areas of crime."