Police have confirmed that a 35-year-old man from Newhaven died at the scene of the collision.
The collision happened near the junction with the A26 New Road and the B2109 Avis Road at South Heighton just after 10am.
A 65-year-old man from Bishopstone was taken to the Royal Sussex County Hospital in Brighton with serious injuries.
Both men were pedestrians.
The driver of the red dropside DAF lorry, a man from Kent, was uninjured. He was driving south on the A26 when the incident occurred.
Both the A26 and B2109 roads remain closed while investigation and recovery work takes place. It is hoped that the scene will be clear and reopened by mid-afternoon.
Anyone who witnessed the incident is asked to email email@example.com or call 101 quoting Operation Glinsk.
Slow traffic and road closed due to accident, two cars involved on A415 Abingdon Road both ways between B4449 Aston Road and High Street / Shifford Lane. Closed from Standlake Caravan Park.
The owner of a mobile home was killed when a mystery blaze swept through the unit causing devastating damage.
The motorhome, which was based on a caravan park, caught fire shortly before 10pm on Thursday evening and the victim's body was discovered inside by firefighters.
The alarm was raised when smoke and flames were spotted coming from the mobile home in Chipping Norton, Oxfordshire.
Four fire crews raced to the scene but were unable to save the occupant whose body was discovered inside.
Police said that the death was being treated as unexplained.
It was not yet known whether the victim was a man or woman and it was suspected that body may have been consumed in the fire.
The cause of the blaze was not thought to be suspicious.
The fire broke out at the Merryweather Caravan Park in Chipping Norton, and a Thames Valley Police spokesman said the force was informed of the fire in Hook Norton Road, at 10.12pm.
"A body was discovered at the scene but identification is yet to take place. Next of kin have been informed," said the spokesman.
"At this stage of the investigation the death is being treated as unexplained but not suspicious."
Now Christmas Day wouldn't be the same without turkey, crackers and of course Downton Abbey. It's set to hit out screens for a special episode next Thursday. Last year fans of the series were shocked when Matthew Crawley, Lady Mary's husband died. So is Christmas at the real Downton - Highclere Castle in Hampshire - as dramatic? Mel Bloor has itsstory.
Gatwick-bound travellers were held up for a third morning running by problems on the railway.
The latest difficulty for those heading to the West Sussex airport by train was caused by a signalling problem at Burgess Hill in West Sussex.
As well as affecting the Gatwick Express services, the problem caused delays to trains run by the Southern and Thameslink companies.
There were other delays during the morning rush-hour. In Kent and East Sussex, signalling problems between Ashford International and Rye caused hold-ups.
Two brothers have been jailed for life for murdering a Hampshire shopkeeper.
Choudhry Zishan, who was 35, was killed outside his shop in Eastleigh High Street in March.
Brothers Jonathan McKinley, 23, and his brother Samuel, 25, denied killing Mr Zishan but were found guilty of murder.
They have been told they must serve a minimum of 28 years.
Marylebone station has a giant ice sculpture on show to celebrate Christmas. It shows the Radcliffe Camera Building, Dreaming Spites of Oxford along with Big Ben and Chiltern Railways train to mark new services from Oxford Parkway to Marylebone next September.