By William James

LONDON (Reuters) - Prime Minister Theresa May set out a drive to tackle modern slavery in Britain on Sunday, pledging more funding and a new cross-government taskforce to help stamp out what she called a "barbaric evil".

She made the pledge as a review into the 2015 Modern Slavery Act, pioneered by May in her previous role as interior minister, showed that in 2015, 40 percent more victims had been identified and 14 percent more slavery offences had been prosecuted.

Nearly 46 million people are enslaved globally, according to the 2016 Global Slavery Index, which estimated there were 11,700 victims living in Britain.

"From nail bars and car washes to sheds and rundown caravans, people are enduring experiences that are simply horrifying in their inhumanity," May wrote in the Sunday Telegraph newspaper.

"This is the great human rights issue of our time, and as prime minister I am determined that we will make it a national and international mission to rid our world of this barbaric evil," May said.

The International Labour Organisation estimates that forced labor generates global profits of about $150 billion per year, mainly from the Asia-Pacific region and developed economies, including the European Union.

May, who took office earlier this month, said 33.5 million pounds ($44.32 million) of the overseas aid budget would be put into a five-year fund designed to tackle the issue in countries, like Nigeria, which are the source of proven human trafficking routes into Britain.

May also said she would set up a taskforce that would hold regular meetings "to coordinate and drive further progress in the battle against this cruel exploitation".

The Modern Slavery Act, seen as a milestone in the international fight against slavery, requires businesses to disclose what action they have taken to ensure their supply chains are free of slave labor. It also introduced tougher criminal sanctions for perpetrators and more victim protection.

A year after it was introduced, a review found a 289 slavery offences had been prosecuted in 2015, up from 253 in 2014, while the number of referrals to the national support system for victims had risen to 3,266 from 2,340.

The review's author, barrister Caroline Haughey, welcomed the impact of the new laws, but said more needed to be done to make sure they were being applied consistently across the country.

($1 = 0.7559 pounds)

(Reporting by William James)