Under Kuwaiti law, a minister automatically becomes an ex-officio member of parliament with the same rights as elected MPs except for votes on no-confidence motions against ministers.
As al-Mubarak began to take her oath on Monday, a number of Islamist and tribal MPs opposed to women's political rights began screaming and banging on their desks. But she looked unbothered as she continued to read the oath.
The MPs said al-Mubarak's appointment was unconstitutional because she has not been registered as a voter. They said electoral law requires members of parliament, including ministers, to be registered voters.
Al-Mubarak could not register as a voter because annual voter registration opens only in February, but women were not enfranchised until May.
Parliament Speaker Jassem al-Khorafi, however, told the house that he had studied the matter with constitutional experts who said her appointment was legal.
A small crowd in the gallery, including women, witnessed the historical oath-taking, but the event was recorded to be broadcast on state-run television later on Monday.
Liberal academic al-Mubarak was among the first ministers to arrive at the parliament building and sat in the front row next to other cabinet members.
"It's a great victory. It's a glorious victory for Kuwaiti women and a glorious victory for democracy," al-Mubarak told reporters as she walked through parliament gate.
Al-Mubarak, who was appointed minister for planning and administrative development on 12 June, was sworn in on Saturday by Deputy Amir and Crown Prince Shaikh Saad Abdallah al-Sabah.
Some fellow ministers opposed
After taking the oath, al-Mubarak delivered a speech in which she thanked Kuwait's Amir Shaikh Jaber al-Ahmad al-Sabah, currently in the United States for treatment, for his initiative to grant women full political rights.
"It's a great day for Kuwaiti women who struggled with determination and resolve to secure their full [political] rights," she said.
Some Islamist MPs said they would file a request to refer al-Mubarak's appointment to the constitutional court. Khorafi refused to accept the request because Monday was a special session to discuss the budget.
The request is likely to be submitted next week.
The government, in a landmark decision two weeks ago, appointed two women to Kuwait's 16-member municipal council, a body whose functions are limited to monitoring civic planning, some public services, restaurants, roads and civil construction.
Kuwaiti women will make their election debut in the 2007 legislative elections and vote in and contest the next municipal polls in 2009, after parliament voted on 16 May to grant them full political rights.