Commonwealth Secretary General Don McKinnon said Pakistan had been suspended from the 53-nation group "pending restoration of democracy and the rule of law."
The organization had set a deadline for President Pervez Musharraf to lift a three-week-old state of emergency and step down as army chief. Musharraf announced a state of emergency on November 3, citing increasing militant activity.
U.K. Foreign Secretary David Miliband said the Commonwealth would hopefully soon be able to readmit Pakistan if it met the organization's demands, adding that the decision to suspend the country had been taken "in sorrow, not anger."
Pakistan's Supreme Court dismissed on Thursday opposition claims over the legitimacy of Musharraf's reelection for a second five-year term following indirect presidential elections on October 6.
In 2005, the Commonwealth gave Musharraf two years to resign from the military. Pakistani Attorney General Malik Qayyum said this could happen as soon as the weekend.
In 1972, Pakistan quit the Commonwealth until 1989 when it returned to the organization under the leadership of Benazir Bhutto. In 1999, the Commonwealth suspended Pakistan for four years after General Musharraf seized power in a military coup.