Egypt, which depends heavily on imports, is facing a foreign currency crisis and is under increasing pressure to devalue the pound, but the central bank surprised markets when it strengthened the pound by 20 piasters in November and has held it steady ever since.
The central bank sold $38.8 million at a cut-off price of 7.7301 pounds to the dollar on Thursday, unchanged from the previous auction.
But the black market rate jumped, with traders quoting 9.50 pounds to the dollar, compared with a range of 9.30 to 9.34 to the dollar on Tuesday.
Trading for dollars in the black market is now limited to regular customers, traders said, with many exchanges fearing a crackdown after several were closed down in February.
Egypt has been starved of foreign currency since an uprising in 2011 ousted autocrat Hosni Mubarak but drove away tourists and foreign investors - major sources of hard currency.