The queen expressed her gratitude for the honour offered to her son, but prayed for time before giving a decided answer, in order that she might consult the ministers of her religion as to whether such a marriage might be entered into, by one of the Reformed religion.
The news of the proposed marriage, and also of the negotiations that had been opened for a marriage between Elizabeth of England and the Duc d'Alencon, created the greatest alarm throughout the Catholic world.

A legate was sent to Charles by the pope, to protest against it.

Sebastian, King of Portugal, who had refused the hand of Marguerite when it had before been offered to him, reopened negotiations for it; while Philip of Spain did all in his power to throw obstacles in the way of the match.
The ministers of the Reformed religion, consulted by the queen, considered that the marriage of Henry to Marguerite would be of vast benefit to the Huguenot cause; and declared that a mixed marriage was lawful.

The English ambassador gave his strongest support to it, and the Queen of Navarre now entered upon the negotiations in earnest, and went to Blois for the purpose.
The differences were entirely religious ones, the court insisting that Henri, while living at Paris with his wife, should consent to be deprived of all means of worshipping according to his own religion; while Marguerite, while in Bearn, should be guaranteed permission to have mass celebrated there.

The king would have been ready to waive both conditions; but Catherine who, after at first favouring the match, now threw every obstacle in its way, was opposed to any conclusion.