Kuwait's constitutional court on Wednesday declared February's legislative polls in which the opposition swept to victory illegal and reinstated the previous pro-government parliament.
Leading opposition MP Mussallam al-Barrak described the verdict as "a coup against the constitution" and called for the opposition to take a united stand.
"The court nullifies the election that was held on February 2, 2012... and cancels the membership of MPs who were declared winners," said the court verdict, a copy of which was obtained by AFP.
The court based its decision on the grounds that two decrees "dissolving the previous parliament and calling for a fresh election were illegal," the verdict said.
The ruling, which is final and cannot be challenged, also stipulated that "the previous parliament regains its constitutional powers as if it had not been dissolved".
The government held an emergency session and studied "measures needed to implement the court verdict," Information Minister Sheikh Mohammad Abdullah al-Sabah told a news conference.
The minister said "the objective reasons that led to dissolving the previous parliament are still outstanding" and the cabinet would continue to study the necessary legal measures to enforce them.
The cabinet would continue its meeting Thursday to take the necessary decisions, he added.
At least 16 opposition MPs who were members in the previous parliament announced their resignation from the house, saying in a statement they refused "to sit in a parliament rejected by the people."
Thirteen MPs in the previous parliament were questioned last year by the public prosecutor on charges that they received about $350 million in illegal deposits that opposition MPs charged were bribes.
In early December, the emir, Sheikh Sabah al-Ahmad Al-Sabah, issued a decree dissolving parliament following youth-led street protests demanding reforms and the sacking of prime minister Sheikh Nasser Mohammad al-Ahmad al-Sabah.
Following the resignation of Sheikh Nasser in late November, the emir appointed Sheikh Jaber Mubarak al-Sabah as new premier, but he "left the previous cabinet intact, which is illegal," lawyer Yacoub al-Sane told AFP.
A few days later, the emir issued another decree inviting Kuwaitis to elect a new parliament on February 2.
Sane said it was the "illegal" cabinet which recommended to the emir to dissolve the previous parliament and to call for elections, thus rendering the procedures illegal.
The unprecedented ruling is expected to plunge the oil-rich Gulf state into a new political crisis. Kuwait was rocked by a series of political crises since 2006 during which eight cabinets resigned and the parliament was dissolved on four occasions.
Political analyst Anwar al-Rasheed said the ruling will escalate already high political tension in Kuwait unless the emir dissolves the reinstated parliament again and calls for new polls.
"This historical ruling will certainly lead to intensifying the political crisis in the country that has been suffering for a long time," Rasheed told AFP.
The Kuwaiti ruler on Monday suspended the opposition-controlled parliament for one month in a bid to ease the situation after two ministers were forced to quit from the four-month old cabinet.