One of Britain's most senior police officers attacked retailers after Black Friday promotions sparked chaos and violence in stores around the country.
Sir Peter Fahy, chief constable of Greater Manchester Police (GMP), condemned lax security arrangements at shops after fights broke out and huge crowds threatened to cause crushes.
Officers were called to a number of supermarkets overnight amid chaotic scenes as thousands of shoppers sought discounts.
At least three people were arrested and a woman was hurt after being hit by a falling television, while some outlets were forced to shut to restore order.
Eyewitnesses described how bargain-hunters behaved "like animals" and likened scenes to "a war zone".
Sir Peter, whose force appealed to shoppers to "keep calm", said: " The events of last night were totally predictable and I am disappointed that stores did not have sufficient security staff on duty.
"This created situations where we had to deal with crushing, disorder and disputes between customers. It does not help that this was in the early hours when police resources are already stretched.
"Across Greater Manchester large supermarkets already make significant demands on policing through calls to shoplifting, anti-social behaviour and thefts of fuel from their petrol stations - much of which is preventable.
"We just ask these stores to work with us to reduce the demands on policing and reduce the risks of disorder and crime."
A number of outlets around the country opened at midnight as chains offered big price cuts to mark Black Friday, a phenomenon originating in the United States which has emerged as one of Britain's busiest shopping days of the year.
GMP said officers were called to seven Tesco stores across the area. A post on the force's Twitter feed said: "Keep calm, people!"
Shortly after midnight a 42-year-old man was arrested on suspicion of assault at a Tesco on Burnage Lane, Green End.
Another man was arrested on suspicion of a public order offence after police were called to reports of fighting between some in a 300-strong crowd at a Tesco on Stockport Road, Hattersley.
A third man was arrested shortly after 1am at a Tesco on Woodrow Way, Salford, after he threatened to "smash" a shop worker's face in, police said.
Officers were called to four other Tesco branches across the area to deal with large crowds, including in Stretford, where fights broke out and a woman suffered minor injuries after being hit by a falling television.
Police were called to three Tesco branches in London following reports of large crowds in Edmonton, Willesden and Surrey Quays.
Images posted online showed chaotic scenes in Edmonton, with witnesses describing "mayhem" as discounted coffee machines went on sale.
Metropolitan Police Sergeant Paul Marshall said on Twitter: "Even on Black Friday shoving people to the floor so you can get £20 off a coffee maker is still an assault."
Footage from Asda in Wembley, north west London, showed security staff struggling to contain a crowd of shoppers grappling for cut-price televisions.
Some customers had to be separated as the sale sparked furious exchanges, while two women were seen wrestling over a TV.
As the doors opened at the store this morning, at least one woman was knocked to the ground in the rush.
South Wales Police also reported receiving a number of calls from staff at Tesco stores after they became "concerned due to the volume of people who had turned up to sale events".
Officers went to a store on Excelsior Road in Cardiff twice after midnight over concerns about "customer conduct", police said, adding that no arrests were made.
There were also disturbances in Scotland. Police were called to Tesco at Silverburn in Glasgow which was closed for a period as people clashed over discounted goods.
At another Tesco store in Dundee, police were called to similar scenes and a decision was taken by staff to shut the shop.
Those seeking cut-price deals online also faced problems, with shoppers struggling to access the websites of Tesco Direct, Currys, Argos and GAME this morning.
A Tesco source insisted they "work closely" with police and take guidance on security measures in stores, adding: " We will work with them following this event to make any improvements for next year."
The supermarket chain had touted the promotion as "its biggest ever Black Friday event", with discounts of up to 70% on 200 electrical, entertainment, DIY and toy products.
Tesco said in a statement: "Over 600 Tesco stores have Black Friday offers available in store.
"In the interest of customer safety a small number of these stores contacted police last night to help control crowds safely and stores are now trading normally."
Asda said its stores were visited by more than two million customers with "many more" expected throughout the day.
A spokeswoman added: " We do not condone the behaviour of a very small number of people in our Wembley store this morning.
"Despite our extensive planning and additional security colleagues there was an isolated incident this morning when the store opened. The sale has run smoothly in all our other 440 participating stores."
West Yorkshire Police confirmed officers were called to reports of a disturbance at the Tesco store in Batley, near Leeds.
A spokesman said the officers were alerted at 11.50pm yesterday.
He said police monitored what happened but no offences were committed and no arrests were made.
Deputy Chief Constable Sue Fish, national policing lead for business and retail crime, said: "This year stores have increased their marketing around the sales on Black Friday but they don't appear to have worked effectively with their security teams to ensure that sufficient security arrangements are in place to deal with the number of customers.
"Better co-ordination between marketing and security departments in stores planning sales like this will prevent police having to direct resources from other areas of policing to step in and help with shop security."