Egypt's new constitution "prepares the way for an Islamic caliphate", according to the acting leader of Coptic Catholics, who is among three bishops to condemn the document as a fundamental attack on human rights.

Expressing their profound disappointment with the constitution signed into law on 26 December, the bishops said only extremist Muslims' rights were guaranteed by the new document and that at particular risk were women, young people and religious minorities.

Bishop Kyrillos William, Administrator of the Coptic Catholic Patriarchate of Alexandria, said: "We were waiting for a constitution that represents the whole of Egypt but instead we have one that only represents one group of people.

"We can see that the religious orientation of this constitution prepares the way for an Islamic caliphate."

Bishop William was among three Coptic Catholic bishops including Joannes Zakaria of Luxor and Antonios Aziz Mina of Giza who told Catholic charity Aid to the Church in Need that the constitution was a threat to civil liberties.

Bishop William said: "Everywhere in the constitution there are clauses saying everything should be in accordance with Islamic law.

"The president [Mohammed Morsi] promised to build a civic, modern and democratic state but we do not think that this constitution is in any way in accordance with that."

Among the bishops, there was concern that the constitution would force non-Muslim women to wear Islamic headscarves and would legitimise the marriage of under-age girls.

The bishops said that, apparently in line with Shari'a law, the constitution permits women who are "sexually mature" to marry, which they said strongly implies acceptance of teenage marriages.

Bishop Zakaria said: "The Islamists want to apply Shari'a law especially with regard to women. It is very bad for women and very bad for non-Muslims in society."

Saying that the constitution is "not good news" and "does not take into consideration human rights for all", Bishop Aziz said the constitution implicitly sanctions child labour, only warning against forcing youngsters to do work that is too demanding for them.

Citing Article 219, Bishop William said: "The constitution not only outlines the principles of Shari'a but describes in detail all of the values and opinions contained in the Shari'a. It will be terrible – everything will be interpreted according to Shari'a."

The bishops said that this heavy insistence on Shari'a undermined the credibility of Article 3 in the constitution which asserts the rights of Christians and Jews as well as Muslims.

Describing the constitution as the work of fundamentalist Muslims, Bishop Zakaria said: "It was already hard to get permission to repair a church in [former] President Mubarak's time, now it will be ever harder.
"But it will be much worse for Shiite Muslims, Baha'is, Buddhists and others who are not even recognised in the constitution."

Both Bishops William and Aziz accused the government of severe electoral malpractice in last month's constitution referendum and that with a voter turn-out of only 33 per cent the President had no right to pass it into law.

Bishop William referred to reports that ballots slips rejecting the constitution had been found in toilets and that pro-constitution campaigners had bribed voters with oil, rice and other goods.

The referendum followed long-running controversy over the drafting of the constitution.

The Coptic Orthodox Church withdrew in April 2012 from the talks on the constitution in protest at the reportedly Islamist content proposed. Coptic Catholic and Protestant representatives quickly followed suit. Secular parties also later pulled out.

The bishops said that the parliamentary elections due later this year will be a vote of confidence on the new constitution and the government's handling of it.

Bishop William said: "The people should fight for their rights. The Church cannot speak in their name but we can make people aware of the issues through our Justice and Peace committees."