The US private equity group Blackstone has sold more than 3,000 shared ownership homes to Britain’s biggest private pension fund in a £405m deal, the latest by big investment companies in the UK housing sector.

The New York-based company sold the portfolio to the academia pension fund, the Universities Superannuation Scheme (USS), which manages more than £75bn of assets.

The sale is one of the biggest in the UK housing sector this year, and the largest involving shared ownership homes since the creation of the shared ownership scheme in 1990.

The scheme allows people who cannot afford to buy a home outright to get on the property ladder by buying part of it, with the option of acquiring the remainder in the future.

The scheme is open to people whose household income is up to £80,000 a year, or up to £90,000 a year in London, and if they cannot afford all of the deposit and mortgage payments “for a home that meets your needs”.

Blackstone has been investing heavily in rental and social housing, and agreed to buy 1,750 rental homes from the housebuilder Vistry for £580m in June.

The firm has ramped up investments in British housing, betting on long-term returns in a market where demand far outstrips supply in a long-running housing crisis that experts say will take more than a decade to fix.

The new Labour government has promised to build 1.5m new homes over the next five years, with a focus on affordable housing, in particular social homes, and laid out changes to the planning system.

Blackstone sold the homes via its Sage Homes vehicle, a housing joint venture with the private equity investor Regis Group that was launched in 2017.

The portfolio, which is located across the UK, consists of shared ownership properties across 250 Sage Homes sites. USS has launched Sparrow Shared Ownership, a registered provider of social housing, to manage the homes.

James Seppala, the head of real estate Europe at Blackstone, said the company had “created an institutional-grade portfolio which has, in turn, attracted more long-term institutional capital into the sector”. He said the sale proceeds would be invested in Sage to help alleviate the undersupply of housing in the UK.

“Through Sage Homes, which was established in 2017, Blackstone has been the largest provider of newly built affordable housing in the country for the last three years,” he added. Sage has committed £3.7bn to fund the development of 22,600 affordable rent and shared ownership homes, of which more than 17,000 have been built so far.

Institutional investment in UK housing is still small compared with the US and continental Europe, and makes up just 2% of the total rented stock, compared with more than 35% in Germany and the US, according to Savills.