Baroness Helena Kennedy, QC, said Kenny MacAskill had a choice between using Holyrood's powers to create world-leading legislation, or piggybacking on what she feels is a second-rate Westminster alternative.
There are concerns the Westminster bill, due to be published tomorrow, will not adequately protect trafficking victims. A Scottish bill could make it impossible for police to criminalise someone who has been trafficked, the victim, even if they have committed a crime.
Urging him to take a distinctive Scottish approach rather than accept a Commons hand-me-down, the Glasgow-born Labour peer said Scotland had shown the way on moral issues through the ages, and should do so now on people trafficking.
She said: "Scotland often grasps the nettle more quickly than other places. For example, it was the first place in the world to legislate against torture.
"We've had the memorial to Nelson Mandela. Scotland was outspoken on the whole apartheid regime and more active on that issue than anywhere else early on.
"Scotland has also taken the lead on domestic violence - it was Scotland that invented the Zero Tolerance campaign in Britain.
"On lots of these moral issues, Scotland has ended up at the front. The Scottish Government should take the lead on this one too."
In 2011, one victim of human trafficking was identified every four days in Scotland. Many were women forced in prostitution, while some were forced to labour on illegal drug farms.
Because trafficking is secretive by nature and not seen as a high priority by the public, Kennedy said ministers had to take the lead.
"Government has to say, 'It's not visible, but actually, below the surface, it's contaminating everything that we believe in'."
The Coalition Government will tomorrow publish its solution to the problem in the UK - a Modern Slavery Bill intended to consolidate and tighten laws around slavery in a single act.
Its measures include a maximum jail sentence of life for the worst perpetrators of slavery; Trafficking Prevention Orders to restrict the behaviour and movements of slave drivers; a Modern Slavery Commissioner to hold police and public bodies to account over slavery; and companies being forced to ensure none of their suppliers are using slave labour.
However, Kennedy and others fear the bill will be inadequate, will fail to give the victims of trafficking legal rights, and will ultimately be watered down by right-wing Tory MPs.
She said MacAskill had to choose between going along with the Westminster bill with the odd tweak for Scotland, or pursuing specific Scottish legislation at Holyrood.
She urged him to put the Scottish Government's support behind a proposed member's bill already at Holyrood, which was recently put out to consultation by Labour MSP Jenny Marra.
Marra's Human Trafficking (Scotland) Bill would make it illegal to punish trafficked people forced to commit crimes, and improve the piecemeal prosecution of traffickers by creating a new single criminal offence and an associated offence of aiding, abetting or attempting to commit human trafficking.
It would also create a "survivors' service" for victims and make the Scottish Government issue an anti-trafficking strategy agreed by parliament every three years.
Dr Anne T Gallagher, a leading global expert on the international law on human trafficking, has said that, if passed, the plan "would be the most innovative and comprehensive piece of anti-trafficking legislation in the world".
Marra said her proposal was "world-leading" and trumped the Westminster alternative as it was more comprehensive in the way it would help victims and root out traffickers from communities.
A Scottish Government spokesman said: "Human trafficking is a heinous crime and clearly an international cross-border partnership approach is the most effective way to tackle it.
"We will give careful consideration to the UK Government's proposed Slavery and Human Trafficking Bill and explore the possibility of the Bill covering Scottish interests.
"We note Ms Marra's consultation on a proposal for a bill and will give careful consideration to any bill brought forward on human trafficking."