The court ruled the transfer of National Secuity Council chief Thawil Pliensri approved by Yingluck Shinawatra and her cabinet ministers in September 2011 was illegitimate.
They are therefore no longer qualified to remain in office.
Pheu Thai strategist Pokin Polakul told a press conference after the court ruling that the decision to end the status of Ms Yingluck and some ministers ran against Section 181 of the constitution.
Section 181 says: "The outgoing Council of Ministers shall remain in office to perform duties until the newly appointed Council of Ministers takes office".
According to Mr Pokin, there have been moves by a political party, the People’s Democratic Reform Committee (PDRC) and organisations set up under the Constitution to overthrow democracy and elections.
There have also been moves to ruin some prime ministers — from Samak Sundaravej and Somchai Wongsawat to Yingluck Shinawatra. They were leaders of the Pheu Thai Party and its disbanded predecessor People’s Power Party.
Such moves violated the constitution and constituted a new form of coup, Mr Pokin said.
Pheu Thai also accused the Democrat Party, the PDRC and independent organisations of trying to block the next election planned for July 20 and setting the stage for the appointment of an elected prime minister.
Pheu Thai urged people to demonstrate, file complaints and take peaceful action to oppose such moves. The party urged the Election Commission to hold the next general election on July 20.
Meanwhile Noppadon Pattama, a legal adviser to Thaksin Shinawatra, tweeted on Wednesday that it had become clear the checks and balances of the sovereign powers had been destroyed.
"The mandate of an elected government has been curtailed by the judicial branch. Transferring government officials is a prerogative of the executive branch which has the authority to put the right people in the right jobs.
"Thailand is democratic only in name. In terms of content, there is not much democracy because several mechanisms do not come from the people.
"For example, the half-elected Senate are not aware of its status and duties," he said.