Mum shares shocking photo to warn parents about the type of car seat they're using.

A photo showing bruising from a seat belt injury has been shared by a popular blogger as a warning about car safety for children.

Therese, known as ERFMama, posted the image in an effort to encourage parents to use rear facing car seats for their children.

“This is what can happen to you with a seat belt – [to an] an adult,” she said.

The UK based blogger, who writes about car safety, said many parents allow their children to use an adult seat belt “before they are old enough”.

“Maybe it will make you think twice before you decide to jump to the high back booster or just a seat belt on your child – as a rear facing car seat would never do this to the child.

“So wait as long as possible before you take that last step – the high back booster. The children are far safer rear facing for as long as possible.”

In Australia, National child restraints laws state that babies under six months must be secured in an approved rearward facing restraint.

Children over six months old but under four years old must also be secured in either a rear or forward facing approved child restraint with an inbuilt harness.

But before you throw your forward facing seat out, Kidsafe say there is no evidence to suggest rearward facing seats are safer.

“There is nothing to say rearward facing, at this stage, is safer. But it is safe, as is forward facing. Because of the nature of the safety requirements and the devices on child restraints – both are safe,” Christine Erskine from Kidsafe told Mamamia.

The Kidsafe spokeswoman said Australia had a range of “high standard fit for purpose” choices for parents.

“To reassure parents, we have very high standards for child car seats and we have really good design features – which have been crash tested. We have a standard that allows for rearward facing child restraints up to the age of three. So there’s lots of choice for parents.”

However Kidsafe warn that children should stay in a child restraint that fits appropriately for as long as possible

“Don’t graduate from any forward or rearward facing too soon.  It’s the size of the body and the ability of the child to sit up and be comfortable and fit that is the most important thing.”

As a nation of new “big kids” travel to school for the first time this week, Mrs Erskine said school children may still need a booster seat.

“Yes you have got a school uniform on but you should be in a booster seat if your body is too small for an adult seat belt.”

National child restraint laws

(Source: Child Car Seats)

• Children up to the age of six months must be secured in an approved rearward facing restraint

• Children aged from six months old but under four years old must be secured in either a rear or forward facing approved child restraint with an inbuilt harness

• Children under four years old cannot travel in the front seat of a vehicle with two or more rows

• Children aged from four years old but under seven years old must be secured in a forward facing approved child restraint with an inbuilt harness or an approved booster seat

• Children aged from four years old but under seven years old cannot travel in the front seat of a vehicle with two or more rows, unless all other back seats are occupied by children younger than seven years in an approved child restraint or booster seat

• Children aged from seven years old but under 16 years old who are too small to be restrained by a seatbelt properly adjusted and fastened are strongly recommended to use an approved booster seat

• Children in booster seats must be restrained by a suitable lap and sash type approved seatbelt that is properly adjusted and fastened, or by a suitable approved child safety harness that is properly adjusted and fastened.

Mamamia has reached out to the blogger for further comment.