All but two properties behind the barriers were evacuated and a police chief warned that any rescue of those refusing to leave their homes would be complex and dangerous for both them and the emergency services.

Although the blue temporary barrier continued to hold back the thousands of tonnes of water pouring through the gorge in the River Severn, signs that its had buckled and shifted in several places could be seen clearly.

See also:

• LIVE UPDATES: Emergency evacuation as flood barriers breached in Ironbridge - council boss says 'please do not come' to town

• 'Your safety, home and possessions are at risk. Act now' - Emergency evacuations as flood barriers appear to 'buckling' at Ironbridge

• Shropshire flooding gallery: Latest pictures as flooding chaos continues

• Shrewsbury station back on track after lines deemed safe

• Ironbridge residents counting the cost as 'threat to life' warning stays in place

• 'It's a ghost town': People urged to support Shrewsbury firms as residents describe 'draining' days of flooding

• South Shropshire still on flood alert as snow and ice set to hit Telford, Oswestry, Shrewsbury and more

Chris Bainger from the Environment Agency speaking at the incident headquarters by the famous Iron Bridge said the agency was keeping the situation "under as much control as we can" but was preparing for "the worst case scenario" – water getting under the barrier's membrane.

Pumps were getting rid of the water leaking under the barrier but Mr Bainger said the Environment Agency was looking to draft in additional pumps and extra staff from other areas.

The declaration of a major incident saw police officers speak to those remaining in their properties behind the barrier.

Chief Superintendent Tom Harding said that most of the residents and business owners had now left their buildings - some reluctantly, after officers had spoken to them and explained how the situation had changed.

"We now have just two properties which the owners are refusing to leave," he said.

"I have informed those people that any rescue operation would be complex and dangerous, not only for themselves but for the emergency services involved. However we can not order people to leave."

The West Midlands Ambulance Service, leading the emergency service major incident response, brought in its hi-tech mobile command unit and its Hazardous Area Response Team members were also on site.

Shropshire Fire and Rescue Service was also at the scene in force, with its specialist water unit on standby.

Mr Bainger said there was currently no danger of a dramatic surge or a breach of the barrier. But he said that there was the danger that the water could breach the membrane.

Those who left their properties were being given emergency accommodation at The Valley Hotel in the Gorge.

By Rob Smith and Sue Austin