A £50,000 reward is being offered to find the gunman who killed nine-year-old Olivia Pratt-Korbel.
Tory peer Lord Ashcroft, founder and chairman of Crimestoppers, offered the donation through his charity in return for information that leads to the conviction of those responsible for the schoolgirl’s death.
Olivia died after she was shot by a gunman chasing convicted burglar Joseph Nee into her home in Dovecot, Liverpool, at about 10pm on Monday 22 August.
Her mother, Cheryl Korbel, 46, was shot in the wrist as she tried to close the door on the gunman before the bullet travelled behind her and hit Olivia in the chest.
The youngster was rushed to Alder Hey hospital in a critical condition but was later pronounced dead.
Merseyside Police have arrested nine men as part of their investigation but all have since been bailed.
This week, officers have been searching West Derby Golf Club for the two guns used in the attack.
Writing on Twitter, Lord Ashcroft said: “We need to catch the cowards responsible for the death of nine-year-old Olivia Pratt-Korbel.
“I am offering £50,000 for information, given via CrimestoppersUK, that leads to them being jailed.”
Speaking on Monday, which marked three weeks since the shooting, Detective Chief Superintendent Mark Kameen said: “We have made nine arrests and we are building up an evidential picture, but we still need more information and we need to find the guns.
“I would appeal to anyone who has information which could help us with our investigation to come forward.
“This offender and those protecting him are a blight on the community and the impact they have on the decent people of the community is toxic.”
Olivia’s funeral is due to be held at St Margaret Mary’s Church in Knotty Ash on Thursday.
Classmates have been sharing their memories of Olivia and receiving counselling since returning to school after her death.
Rebecca Wilkinson, headteacher of St Margaret Mary’s Catholic Junior School in Huyton, said pupils would be allowed to wear pink nail varnish on Thursday in memory of the time when the schoolgirl tried to hide her hands from her headteacher to conceal her painted nails.
The school leader said Olivia “oozed kindness” and would be remembered for her smile, adding: “She’d walk into my room with her friends and that smile would just light up the room.”
Anyone with information can call Crimestoppers, anonymously, on 0800 555 111.
Additional reporting by Press Association