CAIRO, EGYPT — Opposition lawmakers boycotted an opening parliamentary debate yesterday on constitutional amendments they say will further tighten the Egyptian president’s grip on power.

More than 100 lawmakers from Egypt’s largest Islamist opposition group, the Muslim Brotherhood, and other parties refused to attend the session of the 454-seat parliament because they say the amendments limit judicial monitoring of elections and ban the creation of political parties based on religion — a measure specifically aimed at the Islamic party.

The rights group Amnesty International said the proposed reforms, particularly anti-terrorism statutes they contain, will lead to the “greatest erosion of rights in 26 years.”

The proposal will “enrich the long-standing system of abuse under Egypt’s state of emergency powers and give the misuse of those powers a bogus legitimacy,” Amnesty International said in a statement Saturday.

In December, President Mubarak asked the legislature to amend 34 articles in the constitution as part of a political reform package — the first major change in the constitution since 1971. But the opposition, which represents about 25% of the parliamentary seats, says the changes are cosmetic and will pave the way for Mr. Mubarak’s son, Gamal, to succeed him in the next presidential elections.

The legislature, dominated by Mr. Mubarak’s governing party, was expected to pass the constitutional amendments later this week. The amendments will then be put to a referendum, which opposition parties are urging Egyptians to boycott.