Ahmad Zia Massoud, a former special envoy to President Ashraf Ghani and a member of a new coalition called the Grand National Coalition of Afghanistan, said at a press conference on Saturday that Taliban militants are preparing to attack Kabul.
He said government is aware of the plan but according to him it has not done anything to counteract the possibility.
Massoud was fired from his post as the presidentís special envoy for forms and good governance in April last year.
"The possibility that Taliban will attack Kabul or other provinces is not far from the imagination. They are living in coordination; both Taliban and government; on how to work for peace process with the price that they (Taliban) will be able to attack provinces. Therefore, I invite all Kabul people to have all their preparations (in place)," Massoud said.
Massoud said the administration is helping the Taliban financially and even militarily.
"The only source for finance and equipping of terrorist groups particularly Taliban is government itself. They tell the Taliban that we will not do anything with you and when they (Taliban) come they hand over all equipment of military bases to them. We are aware that they (government) are financing the Taliban," he added.
"The president (Ashraf Ghani) should be removed as soon as possible," other members of the coalition Humayun Humayun said.
Government did not comment on the claims. The Presidential Palace recently said the current problems are the legacy of those who are criticizing government for different "reasons".
Massoudís announcement comes a week after hundreds of Taliban stormed Ghazni city, about 180km southwest of Kabul, and held the city under siege for four full days.
No exact details on casualties have been released but some sources say up to 200 civilians were killed. As many, if not more security forces are also thought to be dead.