Workers on Government projects are being exploited across the country, peers have heard, amid calls to further tighten laws against modern slavery.
Baroness Young of Hornsey warned many contract and agency workers employed to work on Government contracts are "particularly vulnerable".
She added there have also been claims of "widespread worker abuse" involving social care staff.
The crossbench peer wants public bodies, which she noted have a combined purchasing power of £45 billion, to join commercial organisations in preparing a slavery and human trafficking statement each year.
They should also include this information in their annual report and accounts as part of efforts to make the information more easily accessible, Lady Young added.
The proposals aim to better inform consumers about which companies are doing their best to eradicate slavery and forced labour from their supply chains.
Lady Young (pictured), moving the second reading of her Modern Slavery (Transparency in Supply Chains) Bill, told the Lords: "Many contract and agency workers end up working on Government contracts and this type of labour is particularly vulnerable to exploitation.
"Anecdotal evidence from NGOs (non-governmental organisations) and trade unions points to worker exploitation on Government construction contracts in the south-west of England, recycling plants in the North West and in London.
"Social care contracts are another area of concern. There have been cases of exploitation of workers in the care industry, and allegations of widespread worker abuse by some key local contractors have been reported."
Lady Young said her proposals are not "totally straightforward", noting it was proving difficult to state which local authorities should have to comply with the transparency measures.
She added: "I know there's an argument that says public bodies are already well regulated in terms of ethical procurement practices."
But Lady Young told peers of an order introduced in the US by President Barack Obama in 2012 which sought to prevent federal contractors and sub-contractors from being involved in a series of activities linked to people-trafficking.
She added: "The insertion of public bodies into the Modern Slavery Act points to the potential of their combined purchasing power of £45 billion to contribute to a real change in behaviour from those operators in the commercial sector that are not on the high street, and thus not instantly recognisable.
"At the heart of this clause is the question of how public bodies can use their purchasing power more effectively to root out enslavement and trafficking in their supply chains."
Crossbench peer Lord Alton of Liverpool voiced his support for the Bill, and warned that children as young as eight are being forced to live as modern day "Oliver Twists" - stealing as part of Fagin-style street gangs.
He said: "Our Modern Slavery Act is exemplary, but in truth we shouldn't get too much into a self-congratulatory mode until we have persuaded every country and every sector of society to play their part."
And he warned that the many unaccompanied children who have fled the war in Syria have become vulnerable to human trafficking and modern slavery.
Lord Alton said: "Indeed this week the Dutch media reported that hundreds of children are living in what they describe as a modern Oliver Twist story, some held against their will, others in thrall to their handlers as they are forced to beg and steal their way around European cities - some just eight years of age.
"Fagin, the Artful Dodger, Oliver Twist, should be the characters of Victorian literature, not 21st century Europe."
He also warned that Nigerian boys are being "lured to England with promises of riches from playing football in the Premier League", but once in the UK are forced into slavery.
And turning to his fellow peers, he warned that "modern slavery is so common in the fashion industry that all of us is probably wearing at least one garment that has been made with some element".
Urging the Bill to be taken up by the Government, Lord Alton said that public contracts amount to some £45 billion a year and provide real leverage to force companies to change their practice.
Labour peer Lord Boateng who was the UK's first mixed-race Cabinet minister and was brought up in Ghana, also lent his support.
He said: "I was brought up in the shadow of two slave forts - I passed them every day on my way to school.
"I am married to a Barbadian descendant of slaves and my late grandfather was a campaigner against a particular form of fetish religion ... which has to this day entrapped girls in a form of slavery to local fetish priests in the Volta Region.
"So for me this issue is intensely personal."
Referring to the famous British abolitionist, Sir William Wilberforce, Lord Boateng urged his fellow peers to once again take a stand against slavery.
He said: "Over the years this House has had to tackle the issue of slavery and it has done so with varying degrees of success. It has done so in certain instances in which sometimes it has been in the pocket of slave masters and slave owners.
"But at the end of the day it always got it right, and isn't that something special? Isn't that something to celebrate and to commemorate?"
Copyright (c) Press Association Ltd. 2016, All Rights Reserved. Picture (c) Philipp Naderer / Creative Commons.