Drivers caught using a phone within two years of passing their test will have their licence revoked under new rules in England, Scotland and Wales.
Penalties for using a phone at the wheel double from 1 March to six points and a £200 fine.
New drivers who get six points or more must retake their practical and theory. More experienced drivers can be banned if they get 12 points in three years.
The tougher punishments come alongside a hard-hitting advertising campaign.
In 2015 - the latest year for which figures are available - 22 people were killed and 99 seriously injured in accidents where a driver was using their phone.
Police forces have begun a seven day crackdown, with extra patrols and an "increased focus" on stopping people using their phones while driving.
About 3,600 drivers were handed penalties in the last co-ordinated enforcement week from 23-29 January, the Department for Transport said.
Adverts aimed at discouraging phone use have been developed by the government's road safety group Think! and the AA Charitable Trust, and will be shown at cinemas and on billboards, radio and social media.
In one, a drunk man suggests he swap places with his sober girlfriend, who is texting while driving him home.
The film ends with the message: "You wouldn't drink and drive. Don't text and drive."
'He didn't even go to prison'Image copyright PAul Newman Image caption Ellen's three granddaughters "still ask for their nanna today", her brother Paul says
Paul Newman's sister Ellen was 46 when she was killed just yards from her house in January 2005.
Speaking to BBC Radio 4's Today programme, Mr Newman said: "She was on a shopping trip, walking back home on a pavement and a car left the road and ploughed into her - up to 30 feet into a field. And we lost a beautiful sister.
"We'd go home to an empty house … it destroyed us. It destroys families - it destroys people".
The young driver was using his mobile phone when he lost control of his car.
"He didn't even go to prison - he was a young lad, quite arrogant, no remorse," said Mr Newman.
Ellen was a fantastic doting mother and grandmother to three lovely girls, "who still ask for their nanna today", he added.
'It wasn't an accident'Image copyright Department for Transport Image caption Emily Carvin: "Everything died on that day because that man decided to pick up his phone."
Emily Carvin's mother Zoe was killed 11 years ago when an HGV driver crashed into her car.
She said her mother was approaching some temporary traffic lights when the HGV came up behind her at 60mph. He had failed to see the traffic lights because he was on his phone.
Zoe died of head injuries after the pillar where the seat belt was fixed caved in on her.
Emily, along with her father Paul and brother Ben, feature in the government's campaign.
"People use the word accident," Paul says in a film, Life without Zoe.
"It wasn't an accident. It didn't come about by accident. It was a road crash caused by somebody doing something that he shouldn't have been doing."
"I often talk to her, telling her about things that have happened...things that the children have done, how proud she would have been."
Ben adds: "There's nothing so important that it cannot wait. Don't use your phone."
Transport Secretary Chris Grayling said: "It may seem innocent, but holding and using your phone at the wheel risks serious injury and even death to yourself and other road users.
"Doubling penalties will act as a strong deterrent to motorists tempted to pick up their phone while driving and will also mean repeat offenders could find themselves banned from our roads if they are caught twice."
Calls to prevent drivers using phones intensified last year in the wake of several high-profile cases and research indicating that it was widespread.
In October, lorry driver Tomasz Kroker, who killed a mother and three children while distracted by his phone, was jailed for 10 years.Image copyright INS Image caption Lorry driver Tomasz Kroker killed four people while distracted by his phone
Edmund King, president of the AA, said too many drivers were addicted to their phones.
"We need to break this addiction and the best way is for drivers to go cold turkey - turn off the phone and put it in the glove box."
Chief Constable Suzette Davenport, National Police Chiefs' Council roads policing lead, said: "We need people to understand that this is not a minor offence that they can get away with."
What is the law?
- It is illegal to drive or ride a motorcycle using hand-held phones or similar devices
- The rules are the same if you are stopped at traffic lights or queuing in traffic
- It is also illegal to use a hand-held phone or similar device when supervising a learner driver or rider