The Environment Agency issued the warning as the River Severn level continued to rise during the day, leading to the agency and Telford & Wrekin Council urging residents to leave their homes.
Days of heavy rainfall have pushed defences to the limit, with the barriers along The Wharfage at risk of "overtopping".
However, despite the stark warnings, residents have said they're not planning to go anywhere.
Graham Hickman, who lives in a flat in a building adjacent to the village side of the bridge, said he had lived there since 1950 and the worst flooding he had seen was in 1960.
He said: "I won't be moving it is quite elevated here so I don't think it will be a problem but I do remember the floods of 1960 where there were bikes and sheep flowing past the building, I don't think it is going to be any worse than then."
James and Trina Brophy have lived in nearby Broseley for over 30 years and had come to Ironbridge to look after James' elderly relative, Betty Maiden who is 90.
She lives on the other side of the River Severn, where water was lapping up the edge of the bank but said she wouldn't be moving.
She said: "I have lived in this cottage since I was five, we have seen all this before it's only a bit of water, I wouldn't feel comfortable moving out even for a couple of days, I like it this side of the river."
Although many shops and businesses were closed for the day, Eley's at Ironbridge which sells pork pies, pasties and cakes was open.
Manager Michael Hill said they had been doing a good trade all day. He said: "I think the worst of it is going to be tomorrow (Tuesday) so we will have to take a decision then but it's not my shop I just manager it so we'll see what happens.
"Certainly we have been doing well today with plenty of visitors moving around the place."
Councillor Shaun Davies leader of Telford and Wrekin Council has been working with emergency services, and said it was vital that residents along The Wharfage leave their properties as there was a danger to life.
"The Environment Agency has declared a critical incident and we have made available hotel rooms so that people can be safe and warm over the next couple of days. There is a real risk that water levels will over top the barriers and we do not know what the effect of the force of the water would have on properties.
"This will be as bad as, if not worse than 2020, which, we were told, was a once-in-a-100-year event."
The authority expects around 60 properties to be affected by flooding.
Telford & Wrekin Council has also closed The Wharfage (to vehicles only), The Lloyds, Coalford and Ferry Road, while Madeley Road - originally due to be closed until mid-April for essential roadworks - has reopened with temporary traffic lights.