The speaker of Egypt’s parliament has criticized the “flagrant interference” behind Cairo’s decision to lift a travel ban on American democracy workers accused of receiving illegal funds, echoing growing anger over the move.

The decision to allow the eight Americans, part of a group of 15 foreigners, to fly out of Cairo on Thursday defused the first diplomatic standoff in decades between the United States and Egypt, but raised questions from politicians over possible pressure by the ruling military on judges.

Saad al-Katatni, the speaker of the lower house of parliament, vowed on Saturday that all those involved in the decision would be held accountable.

A special parliamentary inquiry on March 11 would summon the prime minister and other government officials to investigate the circumstances surrounding the decision, he said, as the two houses of parliament convened to draw up the criteria to pick an assembly to write Egypt’s constitution.

“We do not accept any form of foreign interference in Egypt’s internal affairs, under any justification,” said Katatni, who is also a leading official in the Muslim Brotherhood’s Freedom and Justice Party.

“We will not allow anyone, regardless of who it is, to impact the sovereignty of this country and its institutions.”

Mohamed El-Baradei, the former chief of the UN nuclear watchdog and an influential opposition activist, warned interference in the judiciary was a “fatal blow to democracy”.

Egyptian authorities had accused the campaigners, including the son of Ray LaHood, the US transportation secretary, of working for groups receiving illegal foreign funding and prevented them from leaving the country.

Their departure came after days of behind-the-scenes negotiations between Washington and Cairo.

Critics accused the generals, who have ruled the country since Hosni Mubarak was ousted last year, of bowing to US pressure while others say the domestic credibility of officials and the judges who have led the criminal investigation into pro-democracy non-profit groups was increasingly in doubt.