The Design Museum had to take out a £3m loan last year after running an operating deficit without any free reserves in place, the charity’s latest accounts show.
Its accounts for the year to 31 March 2019 show the London-based museum had a total income of £8.7m, but spent £10.8m.
Income levels were down from £10.4m in 2017/18, according to the accounts, which also say that admissions and commercial targets are not being met.
This led to the museum taking out a £3m loan from the Conran Foundation to cover costs, which will be in place until 30 June 2023.
The first repayment is due on 30 June 2021, the accounts say, which the museum hopes will give it time to generate its own reserves through fundraising and operational surpluses.
The museum had 518,000 visitors in the 2018/19 financial year, according to the accounts, but it accepted that it had still maintained an operating deficit that was "not sustainable" in the medium term.
The accounts say that the museum had hired two consultancies to lead strategic reviews of the museum’s philanthropy and business plan, with the aim of achieving operational profitability in the next four years.
The Design Museum has also been lobbying the government for increased statutory funding in line with other major museums, the accounts show.
The museum has been based in Kensington for the past two-and-a-half years, winning a European museum of the year award in 2018 and welcoming more than 1.5 million people since moving to its new site, having previously been based at a former warehouse near Tower Bridge, London.