Labour has challenged the Government’s estimate of how many Afghans who could be eligible for resettlement in the UK are left in the country as the party’s own MPs are already tracking 5,000 cases.

Defence Secretary Ben Wallace previously said he believed between 800 and 1,100 Afghans eligible under the Afghan Relocation and Assistance Policy (Arap) would be left behind, while around 100-150 UK nationals will remain in Afghanistan, although Mr Wallace said some of those were staying willingly.

But in a letter to Dominic Raab, Labour’s shadow foreign secretary Lisa Nandy said 5,000 potential cases had been identified by Labour MPs alone and warned the Government was working with a “serious underestimate”.

The Government has said the Arap scheme is open-ended for Afghans and their families who helped the British effort during the 20-year campaign, and may be at risk of persecution by the Taliban.

Also, the Afghanistan Citizens’ Resettlement (ACR) scheme will allow vulnerable Afghans, such as women and girls, journalists and aid workers, to move to the UK.

The programme will bring 5,000 vulnerable Afghans to the UK in the first year, with up to 20,000 in the long term.

But Ms Nandy said the Government should plan for “significantly larger” numbers.

She said: “My office is currently tracking cases related to 5,000 people from Labour MPs alone, including British nationals, high-profile public figures, people with serious disabilities and children separated from their families – which may give a sense of the complexity of evacuation.”

Ms Nandy said that in the finals days of the evacuation “the only realistic route to assist people was by sending WhatsApp messages to the Defence Secretary or the minister for Afghanistan” as phone numbers and email addresses given to MPs either did not work or were unanswered.

The Observer claimed thousands of emails from MPs and charities highlighting potentially eligible cases went unread by the Foreign, Commonwealth and Development Office (FCDO) amid the chaos of the evacuation.

Ms Nandy also raised concerns with the Foreign Secretary that there had not been agreements with countries neighbouring Afghanistan to accept people wishing to stop there en route to the UK.

She said there was a shortage of safe houses for people in hiding, and aid workers could not use a Government pot called the Conflict, Stability and Security Fund to provide them.

Ms Nandy said: “Now with this new crisis looming, I hope we can work together to ensure they have all the support they need.”

An FCDO spokesperson said: “Our priority has rightly been getting UK nationals and those Afghans who worked for us onto evacuation flights out of Afghanistan.

“In addition, we brought out hundreds of individuals who we identified as special cases due to the particular risk they faced through ties to the UK.

“Now that the evacuation phase has completed we are urgently working through the correspondence we have received on individual cases.

“We have been clear that the Arap scheme will continue and that additional special cases who we called forward for flights but were regrettably unable to evacuate before ceasing operations in Afghanistan, will be guaranteed a place under the new Afghan citizen resettlement scheme.”