Cord Co-Principal Kalonzo Musyoka on Wednesday told government Spokesperson Erick Kiraithe to apologise to two East African countries he claimed were funding opposition activities.
Kalonzo said Mr Kiraithe's statement only works to fuel divisions in East Africa.
The Wiper party leader spoke as he addressed opposition supporters on phone from Beijing China where is attending the World Eminent Chinese Businessmen Association Congress.
The opposition supporters were gathered at Uhuru Park at a rally convened by Cord during Madaraka Day celebrations.
"The government spokesman should forthwith apologise to the countries he accused of funding the opposition to destabilise the government," he said.
The former vice president said allegations made by Kiraithe that the government's of Tanzania and South Sudan were planning a civilian coup against the Jubilee administration should be condemned.
He spoke two days after he again accused the Jubilee government of planning to destabilise the East African Community region.
Last week, Mr Kiraithe caused a stir when he accused Cord of planning a civilian coup against government.
"The government has detailed intelligence reports that some politicians are out to take power through extra-constitutional means," Kiraithe was quoted as saying then.
Similar accusations were made by Jubilee MPs led by Starehe's Maina Kamanda who on Monday accused Cord leader Raila Odinga of planning to take over power through the backdoor.
Cord leader Raila Odinga is a close friend to Tanzanian President John Magufuli.
Former South Sudan President the late John Garang de Mabior was close friend to the former prime minister.