ISLAMABAD - Pakistan's opposition parties have launched a new platform to begin protests against Prime Minister Imran Khan's government and make a rare denunciation of the military for meddling.

All the main opposition parties signed a statement late on Sunday announcing a single platform, the Pakistan Democratic Movement, to begin nationwide agitations, possibly culminating in a January march on the capital Islamabad.

They say the military rigged the 2018 elections to install Khan. The armed forces and government deny that.

"The (military) establishment should stop every kind of interference in politics forthwith," said the statement from the opposition, which accuses Khan of failing on multiple counts from the economy to foreign policy.

"Our struggle is against those who have brought Imran Khan (to power)," former three-time prime minister Nawaz Sharif said by video link to the gathering from London. Sharif was ousted in 2017 amid allegations over his unexplained wealth.

Information Minister Shibli Faraz said the opposition was "ganging up" to pressure the government to close corruption cases, which he said would not happen.

(Reporting by Asif Shahzad; Editing by Andrew Cawthorne) ((asif.shahzad@thomsonreuters.com; +923018463683;))