Migrants being held in the Manston processing centre have begged for help as they described the conditions as a “prison”.

A young girl threw a bottle containing a letter over the perimeter fence to a PA news agency photographer on Wednesday afternoon which claimed there were pregnant women and sick detainees at the Kent facility.

It comes after hundreds of people are thought to have been moved out of the disused airfield site near Ramsgate amid concerns it had become dangerously overcrowded.

The letter, written in broken English and addressed to “journalists, organisations, everyone” appeared to suggest 50 families had been held at Manston for more than 30 days.

It said: “We are in a difficult life now … we fill like we’re in prison [sic]

“Some of us very sick … ther’s some women’s that are pregnant they don’t do anything for them [sic] …

“We really need your help. Please help us.”

The letter claims there is a disabled child at the site, adding: “He’s really bad, they don’t even care about him.

“It’s not easy for someone who has children … There’s a lot of children they shouldn’t be here. They should be in a school not prison,” it adds.

The letter went on to say, “our food is very bad like its make us fill sick … we got no phone no money no smok [sic].”

Witnesses said they saw security guards at the site ushering detainees back inside when members of the press were walking by the fence. The young girl was among a group of children who broke past security guards and ran over to the fence to throw the bottle to the photographer.

The letter added: “We wanna talk to you but they don’t even let us go outside.”

Immigration minister Robert Jenrick said on Tuesday the number of migrants had “fallen substantially”, with more expected to be moved the following day.

The situation had been branded a “breach of humane conditions” with 4,000 people being held there as opposed to its capacity of 1,600.

A Home Office spokesman said: “Manston remains resourced and equipped to process migrants securely and we will provide alternative accommodation as soon as possible.

“We urge anyone who is thinking about leaving a safe country and risking their lives at the hands of vile people smugglers to seriously reconsider.

“Despite what they have been told, they will not be allowed to start a new life here.”

The department said it provides for all the basic needs of migrants arriving in the UK, their safety and those of its staff are its utmost priority and it is committed to protecting their welfare.