Egypt's top court has ruled that the upper house, or Shura Council, and a panel that drafted the new constitution are invalid.
The Supreme Constitutional Court ruled that the laws governing the election of members of the Islamist-dominated Shura Council and the constitutional panel were illegal.
But the court said the Shura would only be dissolved after new elections.
Egypt has faced a string of court cases challenging official institutions.
Islamist President Mohammed Morsi had established the 100-member constitutional panel to draw up the new document.
The constitution was adopted by a nationwide vote in December.
It was unclear what effect the ruling would have on the legitimacy of the constitution.
The Supreme Constitutional Court had ruled last year that the electoral law under which both houses of parliament were elected was invalid, prompting its dissolution.
The Shura Council was then given legislative powers by the constitutional panel.
Mr Morsi's Freedom and Justice party, the Muslim Brotherhood's political wing, holds 42% of the Shura Council's seats and can easily gain a majority with support from conservative allies.
Opponents say the president has used the council to rush through an Islamist agenda and laws that have too many loopholes.
In the latest ruling, the presiding judge, Maher al-Beheiry, said the Shura Council should remain until the election of a new parliament. A date has yet to be set for elections.
There was high security at the court building in southern Cairo ahead of the latest ruling.