Six environmental experts from Afghanistan who were due to attend Cop26 as their country’s delegates to the global conference have had their applications rejected just days before the event begins.

The six – five men and one woman who cannot be named because it could jeopardise their safety – were looking forward to travelling to the event to help make the concerns of Afghans about the climate emergency heard at the summit.

All have fled the Taliban and are in hiding in neighbouring countries from where it would be easy to travel to the UK.

No reason has been given for the six applications being rejected. Initially they thought either the Home Office or the Foreign, Commonwealth and Development Office (FCDO) had vetoed their trip to the UK.

However, FCDO sources told the Guardian the decision had not been made by any UK government department. The United Nations Framework Convention on Climate Change (UNFCCC) secretariat would not be registering delegates from Afghanistan to Cop26 pending further guidance from the Bureau of the Cop, the sources said.

The six, who have previously worked for either UN programmes, the previous pre-Taliban government in Afghanistan or national environmental bodies in their country, say they are very upset with UNFCCC’s decision to bar them from attending this crucial conference.

“We are very disappointed with this decision. We have met all the requirements for the visa but the UNFCCC secretariat rejected our nominations without any proper reasons – maybe due to the ongoing political situation in Afghanistan,” said one of the delegates.

Another said: “By taking this action the UNFCCC secretariat stifled the voice of millions of Afghan victims of climate change impact. Climate change does not respect borders. They should have not mixed the environment with politics. We were hoping to attend Cop26 to raise the voice of millions of Afghan victims of the adverse impacts of climate change.”

While Afghanistan is responsible for only 0.03% of global emissions, the country is severely affected by the climate crisis.

An initial letter to the delegates from UNFCCC secretariat asked for the UK’s assistance to speed up the process of visa applications for the six delegates and to issue them with visas to facilitate their participation at Cop26.

However, a subsequent letter stated: “We are glad to inform you that you have been nominated to attend UNFCCC session Cop26 on behalf of Afghanistan. However your status at the moment is ‘rejected’.”

The UNFCCC has not responded to repeated requests by the Guardian to explain the U-turn on the six delegates attending the conference.