Family and police have released a video of the moment a lorry driver fiddled with his mobile phone before crashing and killing a mother and three children.

Tomasz Kroker has been jailed for 10 years for causing the deaths of Tracy Houghton, 45; sons Ethan, 13, and Joshua. 11; and her partner’s daughter Aimee Goldsmith, also 11.

This harrowing dash cam footage shows the painstaking seconds in which the 30-year-old scrolled through music at the wheel but then collided with stationary traffic.

Thomasz Kroker was jailed for 10 years Thames Valley Police (Thames Valley Police)

Family and friends wept in the public gallery as images were played at the High Court.

"We urge you to make a personal commitment to stop using mobile phones while driving and make our roads safer for everyone," said Aimee's mother Kate Goldsmith, speaking outside court.

"The 10-year sentence will not ease our pain and suffering. Nor do we believe it will send a strong enough message to those who lack the self-restraint to not use a mobile phone when driving."

Kroker, of Andover, Hampshire, was driving a white Mercedes unit and trailer on the A34 in Oxfordshire when he crashed at 5.10pm on 10 August.

The father-of-one smashed into a Vauxhall Zafira that was being driven by Ms Houghton’s partner Mark Goldsmith and his 13-year-old son Jake.

It was the Zafira that was then shunted into the Corsa, which in turn was forced underneath a lorry in front. It was crushed to a third of its size, the court heard.

Kroker stopped to help at the scene but when asked by his company the following day if he was distracted, he said: “Had radio on. Not tuning it. Not on phone.”

But he pleaded guilty to causing the four deaths at the High Court.

Prosecutor Charles Ward-Jackson said Kroker once signed a driver’s declaration form agreeing to “never use a mobile phone or hands-free kit”.

He added: "The defendant, it is clear, was not looking. It is only 0.75 seconds before the crash that the camera shows the defendant looking up with some horror on his face.”

Defence barrister James Rozier said: "The harm that has been caused in this case is unfathomable."

But he said his client was remorseful, gave assistance at the scene, is a law-abiding citizen and is a “man of good character”.

Judge Maura McGowan said: "No sentence I can impose can do anything to mitigate the terrible and permanent loss those families will feel.

"One can only hope that the publicity surrounding this case will bring greater awareness of the consequences of using a phone, not just to text or to call, but also a phone to play music or use some form of navigation software while driving.”

The Polish expatriate was convicted of four counts of causing death by dangerous driving and given four years, running concurrently, for causing serious injury by dangerous driving.