The victims of human trafficking, including women forced into the sex industry or trapped as unpaid domestic servants, are being unfairly treated as criminals and illegal immigrants, an inquiry has found.

The investigation by Lady Helena Kennedy QC has concluded that the police and immigration authorities fail to see the thousands of women, men and children trafficked into Britain as the innocent victims of organised crime whose own basic rights have been breached.

Kennedy's report to the Scottish office of the Equality and Human Rights Commission (EHRC), published on Monday after an 18-month inquiry, calls on the UK and Scottish governments to introduce legislation and criminal justice policies which will tackle trafficking as a specific crime and support its victims.

She said trafficked people frequently end up being forced to work in prostitution, domestic service, fruit and vegetable picking, food processing, benefit fraud and cannabis cultivation. But the issue is chiefly treated by the authorities as an illegal immigration, sexual offences or crime enforcement matter.

Victims were treated as part of the problem, or their needs and rights sidelined, as detectives focus on the brothel owner or the smuggler, since trafficking victims often emerged in raids for drugs, prostitution or immigration offences. By contrast, a British citizen who had been raped or seriously wounded in a normal setting would be given much greater support.

That had the effect of producing ill-thought out responses to trafficking as a specific crime in itself, largely because responsibility was split between different parts of the system: the UK Border Agency, and the police.

In Scotland, for instance, there were two different legal definitions for trafficking. The Gangmaster Licensing Authority, which investigates forced labour in agriculture, food processing and fisheries, did excellent work but was legally barred from investigating trafficking in other industries where it also occurred, Kennedy said.

In one of 10 formal findings, the EHRC report stated: "Human trafficking legislation in Scotland and in the UK has developed in a piecemeal fashion and is not based on a thorough consideration of how legislation should best deal with the problem.

"This has left human trafficking legislation in Scotland and the UK inconsistent, both internally and in comparison with international law, and has served to limit its scope and impact."

It said the Home Office should lead a new review into the identification and treatment of trafficked people, to ensure the UK had "an independent and transparent identification system which recognises that human trafficking is invasive of the dignity and rights of its victims".

Kennedy found there was a significant "intelligence gap" in the police and enforcement agencies about the scale and nature of trafficking.

"The cultures of the different parts of this world of enforcement are incredibly different. We found that people who are serious victims get treated as if they are criminals," she said.

The commission has recommended much greater research and training on trafficking for law enforcement agencies; much greater integration and intelligence-sharing between different agencies at UK and devolved levels; an anti-trafficking campaign to raise public awareness and among the emergency services; a new human trafficking act in Scotland; and greater efforts to tackle trafficking within the business community and labour markets.

Kenny MacAskill, the Scottish justice secretary, said the devolved government in Edinburgh would closely consider the commission's findings along with two earlier reports into child trafficking by the Scottish children's commissioner, Tam Baillie, and on migration and trafficking by a committee at the Scottish parliament.

"Human trafficking is a particularly horrific and brutal violation of human rights. It has absolutely no place in modern Scotland and the consequences it brings for trafficking victims and the communities touched by these crimes are incredibly damaging," he said.

"We have a collective responsibility to tackling the problem here in Scotland. [The] key to eradicating it is partnership working – whether that is working at a local level or working with international partners to provide a solution."