"We are suffering from discrimination because of our beliefs and political thinking"
Hazem Farouk, member of the Muslim Brotherhood's parliament bloc
Political analysts say the government will use the constitutional amendments to stop the Muslim Brotherhood before it makes electoral gains that could help it mount a serious threat to Mubarak's rule.
Hazem Farouk, a member of the Muslim Brotherhood's parliament bloc, said the latest arrests occurred on Friday when 14 men, including 11 working at his office, were distributing medical supplies in Cairo.
"We were not organising a protest or anything, we were just distributing medical supplies among the poor people," he said.
"We are suffering from discrimination because of our beliefs and political thinking," he said
Farouk said the men were being detained despite an order from a public prosecutor to release them.
The proposed amendments would weaken the role of judges in monitoring elections and give police greater powers of arrest and wide authority to monitor private communications.
Amnesty International urged Egyptian politicians on Saturday to reject the proposals, calling them the "greatest erosion of human rights in 26 years."
"The proposed constitutional amendments would simply entrench the long-standing system of abuse under Egypt's state of emergency powers and give the misuse of those powers a bogus legitimacy," said Hassiba Hadj Sahraoui, deputy director of Amnesty International's Middle East and North Africa programme.
The Muslim Brotherhood operates openly despite being banned since 1954.
Members running as independents hold nearly one-fifth of the 454-seat lower house of parliament.
Authorities and state media accuse the Brotherhood of aiming to establish a religious theology through extremism.
The group, which rejects violence, says it wants a democratic state that does not exclude non-Muslims from power.