"More than 70 women on Kenyan tea farms, owned for years by two British companies, told the BBC they had been sexually abused by their supervisors," the broadcaster said on its website.
The report focused on a Kenyan plantation that at the time was owned by U.K. household goods giant Unilever, and another one that remains owned by the tea group James Finlay & Co.
The BBC spoke with victims who said they had no choice but to give in to sexual demands of managers or lose their jobs. One was reportedly infected with HIV by her supervisor.
Secret filming showed that local bosses had sought to pressure an undercover BBC reporter for sex.
Unilever told AFP it was "deeply shocked by the allegations in the BBC program."
The group added in a statement that it had "worked hard for many years to address the very serious issues of sexual and gender-based violence against women in the tea industry.
"This included improving the gender balance of team leaders, upgrading the grievance handling process and strengthening awareness-raising and training."
Unilever added that it was "very disappointed that the measures put in place to make it easier to report, detect and investigate abuse failed to detect and address the issues highlighted by the BBC."
It said it welcomed "the fact that (new owner) Lipton Teas and Infusions will commission a full and independent investigation into these serious allegations".
Both Lipton Teas and Infusions and James Finlay had yet to respond to AFP for comment.
According to the BBC, Lipton Teas and Infusions has suspended two managers, while James Finlay & Co said it had suspended one manager and was investigating whether its Kenya operation faced "an endemic issue with sexual violence."
Unilever last year completed the sale of its global tea business, including the brands Lipton and PG Tips, to the private equity group CVC Capital Partners in a deal worth 4.5 billion euros ($4.8 billion).
It has since been rebranded Lipton Teas and Infusions.