There have been growing calls for action after a Brisbane couple and their unborn baby were killed when a teenager allegedly crashed a suspected stolen car on Australia Day.

On Friday night a Townsville motorcyclist was killed when she was hit by a car being driven by a vigilante, who had been chasing down a alleged stolen car being driven by teenagers.

The premier has appointed former police anti-terrorism commander Assistant Commissioner Cheryl Scanlon to lead a new youth crime taskforce co-ordinating the crackdown.

“The loss of four innocent lives cannot go unanswered,” she said in a statement on Tuesday.

“It is clear to me and to the community that some young offenders simply don’t care about consequences. It’s this 10 per cent who are responsible for 48 per cent of the crime.

“They’re the ones we are going to target with all the force and resources at our disposal.”

Assistant Commissioner Scanlan served as a police officer for 33 years and worked in child safety before heading the state’s Security and Counter Terrorism Command and is “the perfect choice” to lead the operation, Ms Palaszczuk said.

The government will make the announcement later on Tuesday along with a number of other measures to tackle youth crime.

The issue has become highly charged following the deaths of Kate Leadbetter, who was pregnant, when she and her partner Matt Field were struck by an allegedly stolen car driven by a teenager in Alexandra Hills on January 26.

Calls for reform increased with the death of Jennifer Board, 22, at Thuringowa on Friday night after she was hit by a Holden Statesman, which had allegedly been following a stolen Hyundai sedan during a suspected vigilante pursuit.

A 25-year-old Bushland Beach man who was allegedly driving the Holden was arrested on Monday and charged with murder.

Two 18-year-old men, from Rasmussen and Garbutt, were also charged over the fatal crash.

The state opposition has focused its criticism of the state’s youth justice system on what is says are lenient breach of bail laws.