Brait, which also owns gym chain Virgin Active and British supermarket Iceland Foods, said NAV totalled 27.1 billion rand (1.5 billion pounds), or 57.3 rand per share, in the year to end March.
That NAV -- a key performance measure for investment companies that reflects the value of underlying assets excluding liabilities -- was down from 37.8 billion rand, or 77.6 cents a year earlier.
The company said it would not pay a dividend this year because it would use the money to pay down debt.
Shares in Brait fell 1.2 percent to 36.80 rand as of 1029 GMT, bring losses over the last two years to nearly 70 percent.
Brait has been under pressure in recent months as a weaker British pound hit earnings measured in rand, while weak consumer demand and tough competition in UK's high street has weighed on one of its biggest profit sources, New Look.
It slashed the carrying value of New Look to zero in November last year from 7.1 billion rand. Three years ago, New Look was reflected in Brait' books as being worth 35 billion rand, contributing 45 percent to the company's overall NAV.
New Look had been one of Britain's most popular retail names for decades, offering fashionable clothes at lower prices, but it has seen its sales slide over the past year amid rising competition from the likes of online retailers Asos and Boohoo, leaving it forced to close stores.
"New Look's turnaround plan is now well underway and has already made substantial operational improvements to help stabilise the business, reduce its fixed cost base and attain a better position to drive full price sale," Brait said in the results filing.
Brait's woes are another headache for South African businessman Christo Wiese, the biggest shareholder in Brait, after a share price crash in Steinhoff International wiped off billions of rands of his personal wealth.
Wiese backed Brait's purchase of New Look in 2015 in a $1.2 billion deal that put the South African company in the middle of a crowded British high street.
(Reporting by Tiisetso Motsoeneng; Editing by Alexandra Hudson)