The French justice minister has resigned, blaming a "major political disagreement" with her government.
Christiane Taubira stepped down from her job shortly before anti-terrorism proposals that she disagreed with went before parliament.
If passed, the laws would mean that people who are convicted of terrorism offences are stripped of citizenship.
The plans were put forward after the 13 November Paris attacks in which 130 people were murdered.
"I left the government over a major political disagreement," Ms Taubira said.
"I am choosing to be true to myself, to my commitments, my battles and my relationships with other people."
Many of the Islamist militants who carried out attacks in France and have joined the jihadist Islamic State (IS) group have had dual citizenship.
Ms Taubira was among several figures on the left who objected to the government's proposals because they singled out those with dual nationality.
However, the law went before a parliamentary commission shortly after her resignation on Wednesday with no reference to dual nationality.
Prime Minister Manuel Valls presented the revised article of the constitution to parliament, ahead of a debate scheduled to start in early February.
State of emergency
France has been under a state of emergency since the night of the Paris attacks. It allows suspects to be placed under house arrest and for meetings or demonstrations to be banned.
A high court ruled on Wednesday that the state of emergency can continue. A human rights group had challenged plans for its extension, but the judge said "imminent danger" had not gone away. The ruling was made in the Council of State, France's highest administrative court.
Patrice Spinosi, the lawyer for the League for Human Rights, told the French newspaper Le Monde that the persistence of an "unidentified threat" was not enough justification for continuing the state of emergency.
Prime Minister Valls has previously told the BBC that the state of emergency should remain in place "for as long as necessary".
One of France's few senior black politicians, Christiane Taubira, 63, has been replaced by Jean-Jacques Urvoas who is seen as a supporter of the constitutional change and an ally of Prime Minister Valls.
Born in French Guiana, Ms Taubira has suffered racist taunts from the far-right during her time as justice minister.
Her left-wing leanings have put her increasingly at odds with official policy, especially after the November attacks when the president announced a much tougher line on terrorism, BBC Paris correspondent Hugh Schofield reports.
A communique from the Elysee Palace said that President Francois Hollande had accepted the justice minister's decision to resign.
"They agreed on the need to bring her role to an end at a time when debate on constitutional revision begins in the National Assembly, today," the statement read.
In his communique, President Hollande also praised Ms Taubira's part in pushing through same-sex marriage laws.
Darling of the left, by Hugh Schofield, BBC News Paris
President Hollande is going to miss Christiane Taubira because she performed a vital role in his government. Every time he took a move to the right, or was accused of doing so, he could point to his justice minister and say: "Don't worry, Christiane's still with me."
She was his left-wing shield, and he kept her in office to ward off attacks from inside the Socialists over his increasingly pro-business economic policies, and (since November) his tough new line on terror.
Taubira was the darling of the left. Pugnacious and outspoken, she saw through the gay marriage law, and promoted a liberal line on police and sentencing. By the same token, the right despised her and there is now much rejoicing in their ranks.
In the end, President Hollande could no longer pull off the act of political splits which allowed his government to include such mutually hostile forces as Manuel Valls (on the right) and Taubira (on the left).
The times being as they are, it was the left-winger who went.
Last month the justice minister made plain her distaste of the plan to strip citizens with dual nationality of their French citizenship, arguing it "would not help the fight against terrorism in any way".
She said the plan was being dropped only for it be announced the following day by the prime minister with her appearing beside him.
Mr Valls said at the time that it was a "strong symbolic act against those who have excluded themselves from the national community".
He presented the proposals before a parliamentary commission at the National Assembly on Wednesday before they were due to go before MPs next week.
No mention was made of dual nationals, apparently in response to criticism that it could lead to two types of nationality and to people being stigmatised.
However, the French government has made clear that no-one should be made stateless as a result of the reform, implying that it could only ever be used against people with dual citizenship.
Mr Valls told the BBC last week that France could not live forever under a state of emergency but as long as the threat remained all means had to be used "until we can defeat Daesh (so-called Islamic State).
The reforms include the right to declare a state of emergency under the constitution, which would make it easier for the French government to adopt strict powers such as police raids and house arrests.
The government aims to extend the three-month state of emergency imposed after the November attacks when it expires on 26 February.