(Reuters) -Carlyle Group said on Thursday it had raised $20 billion to buy second-hand private equity stakes from investors looking to offload assets that built up during a downturn in public listings and acquisition deals.

The investment firm's AlpInvest unit, operating in the secondary market, raised $15 billion for its latest flagship fund along with $3.2 billion in co-investment commitments, Carlyle said.

A further $2 billion was raised for private wealth vehicles that will invest affluent people's money alongside the main fund, the company said in a statement.

A slowdown in deals led to a build-up of some 29,000 companies valued at $3.6 trillion in private equity firms' portfolios by the end of 2024, according to research from consultants at Bain.

The secondary market has offered a way to get some cash for those assets, albeit usually at a discount to previous valuations.

The value of secondary market assets swelled to $601 billion in 2024 from $273 billion in 2019 and now represents 5% of all private equity assets under management globally, Bain said in its 2025 private equity report.

(Reporting by Isla BinnieEditing by Ros Russell)