The racial disparity audit, which May had commissioned just after she took office a year ago, gives an "unprecedented insight" into how people from different minority backgrounds face a "postcode lottery of outcomes" just like the unemployment rate for ethnic minorities being nearly double that of white British adults in the UK.
The first national survey of its kind found huge gulfs in experience of health, housing and education, which also varied based on geography. Only 54% of white British pupils reach the same standard, and white Gypsy and Roma pupils perform significantly worse at 13%.
One of the key findings is that employment rates are higher for white people than for ethnic minorities across the country, with a larger gap in the north (13.6%) than in the south (9%).
Ethnic minorities are underrepresented at senior levels across Britain's public sector. "But this audit means that for society as a whole -for government, for our public services - there is nowhere to hide".
She will say "these issues are now out in the open" and that the collection of data provides "definitive evidence" of the challenges the United Kingdom still faces to "build a country that works for everyone".
Communities and Local Government Secretary Sajid Javid told Sky News the report showed "there is still more work that needs to be done" as he described the investigation's first phase as a "data collection exercise". But her government has become bogged down with Brexit negotiations and infighting, and May was weakened after her Conservative Party lost seats in a snap election in June.
Black men were also the group most likely to have a drug dependency, while black women had a higher expectancy to suffer from mental ill health. "Tackling inequality will need the devotion of all her ministers", he said.
"That was something where she had the data, analysed it, thought it was unacceptable and just by shining a light on it, it changed practice".
Meanwhile, Labour have accused Theresa May of adding "fuel to the fire" instead of tackling "burning injustices" as the findings of the audit were released.
But critics of the Prime Minister have accused her of using the data for "political point scoring".
Al Jazeera's Paul Brennan reports from London.
The Equality and Human Rights Commission has called for a clear "race equality strategy" as a damning audit is about to be made public, highlighting disparities in the treatment of people of different ethnicities.
He said some statistics made "uncomfortable reading", but that "unless these things are laid bare we can't begin to resolve them".
The Department for Work and Pensions is expected to set up some 20 "hotspot" areas to help ethnic minority individuals find employment.