The group has faced criticism in recent years after its use of suppliers in the UK revealed workers at some were paid as little as £3 an hour.
The decision to sign up to Fast Forward, a sector-leading auditor that already has members including Asos and M&S, comes as Sir Brian Leveson published his latest review into the business.
Leveson, who is leading an independent review into Boohoo’s supply chain practices, said the company’s due diligence may now go beyond some of its rivals.
He added: “In my numerous discussions with… directors and managers at Boohoo, I remain encouraged by the determination of all to address the issues which were exposed last year and to both promote and embed a new way of working to the highest ethical standards.”
Three reports have now been published by the retired judge. Bosses said they remain committed to publishing a global supplier list in September this year and continue to review their entire manufacturing supplier base.
The company’s co-founders, Mahmud Kamani and Carol Kane, said: “We are extremely proud of the incredible amount of change our teams have delivered, with the group making exceptional progress over the last 11 months in developing a robust, fair and transparent supply chain, which is recognised in Sir Brian’s latest report.
“As a group we are on track to meet all of the commitments that we set out last year and we remain committed to setting the bar, to drive measurable and sustainable change.”
Fast Forward was launched in 2014 and aims to uncover audit evasion and hidden exploitation, including forced labour.
It also assesses whether suppliers are potentially breaking employment laws and adhering to ethical labour standards.
The latest plans for Boohoo come as the company revealed the reopening of non-essential clothes shops failed to dampen sales at its online-only operation.
Sales in the three months to the end of May soared 32 per cent to £486.1 million, with the UK seeing the strongest growth across its biggest regions.
Boosts in total sales were in part due to the successful integration of the Dorothy Perkins, Wallis and Burton brands onto its platform after buying them from Arcadia administrators. Boohoo also launched a new online-only Debenhams store, buying the brand rights for £55m.
In both cases, all stores were closed, leading to thousands of job losses.
John Moore, senior investment manager at Brewin Dolphin, said: “Boohoo continues to grow, with its US operation a particular driver over the last two years and UK sales nearly doubling over the same period.
“Of bigger concern to investors, however, has been the ongoing issues over the business’s ethics, sustainability, and supply chain. A year on from the first reports, Boohoo has outlined some of the ways it is addressing these concerns – and that is perhaps reflected in a partially recovered share price.”