New video shows vice president Mike Pence “callously” observing crowded pens of migrants on the US border before turning his back and leaving.

The moment was captured during Mr Pence’s tour of a detention centre in McAllen, Texas, during which he said the system was “overwhelmed” but insisted families were “well cared for”.

He’s shown standing before a crowd room full of migrants, as an official talks to him about procedures at the centre.

As scores of men held behind wire fencing try to catch his attention – with some shouting out how many days they’d been held – he appeared to avoid any eye contact.

His gaze strafed the room above the level at which the men stood. Then, after less than a minute, he turned and left.

'Dangerous' overcrowding of migrants in US border facilities Show all 6 1 /6 'Dangerous' overcrowding of migrants in US border facilities 'Dangerous' overcrowding of migrants in US border facilities Photos of detained migrants crowded into cells at the US border - with one holding up a sign reading simply "help" - have been released as part of a new report warning of "dangerous" overcrowding. The memo was sent to the Department of Homeland Security by its Inspector General, containing photos taken at border facilities in the Rio Grande Valley over a week in June DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Eighty-eight adult males held in a cell with a maximum capacity of 41, some signalling prolonged detention to OIG Staff on June 12 DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Overcrowding of families observed by OIG on June 11, at a border patrol facility in Weslaco, Texas DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Migrant families overcrowding a border patrol facility on June 11 in McAllen, Texas DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Fifty-one adult females held in a cell designated for male juveniles with a capacity for 40 at Border Patrol’s Fort Brown Station DHS/OIG 'Dangerous' overcrowding of migrants in US border facilities Migrant families overcrowding a border patrol facility on June 11 in McAllen, Texas DHS/OIG

Shannon Watson, founder of gun control group Moms Demand, posted the clip to Twitter saying: “This image will go down in history.

“New video shows shows Mike Pence callously observing and turning his back on severe overcrowding of men in cages at a detainment facility in Texas.”

The post was retweeted thousands of times. One person responded: “This is the way a rancher examines a holding pen for cattle. These are human beings.”

Another said: “I saw not a single shred of pity or empathy in that empty man’s eyes. This is truly horrifying to observe in a man who could possibly do damage to our country in the future. We should each of us see ourselves in those men’s shoes, before it’s too late for our souls.”

Mr Pence visited two areas of the border on Friday, beginning with a station in Donna, where air-conditioned, interconnected tents were built in May to temporarily handle 1,000 migrants.

He then went to McAllen where 384 single men are being held behind wire fencing with no beds.