An alliance of opposition groups has urged its supporters to vote No in the referendum on a disputed constitution, but said it may still call a boycott if conditions are not met.

Hamdeen Sabahi, a leader of the opposition National Salvation Front, said the alliance would urge supporters to boycott the vote if judges did not oversee the ballot and the state did not provide security at polling stations. The front did not, however, call for civil disobedience, such as general strikes, to escalate the recent mass protests against President Mohamed Morsi.

The major judges' union has said its members would boycott the referendum and abstain from their traditional role of oversight at the polls.