PC Keith Palmer's murder, in an attack outside the Houses of Parliament in March, prompted "greater emphasis" on the need for a permanent memorial.
The UK Police Memorial Trust appealed for £1.5m towards its construction at the National Memorial Arboretum.
It is set to bear the names of more than 1,400 officers and staff.
Sir Hugh Orde, chairman of the trust, said: "PC Palmer's death has put greater emphasis on the need to create a place where the nation can honour and commemorate our police service and where family, friends and colleagues of those killed on duty can go to carry out personal acts of remembrance.
"We need to establish a fitting memorial that recognises the vital contribution that policing makes to our society and acknowledges the courage and sacrifice made by police officers and police staff who have paid the ultimate price.
"That tribute must become part of the fabric of our national life."
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The memorial, at the site in Alrewas, Staffordshire, will be dedicated to the courage and sacrifice of the officers, who have lost their lives over the past 250 years.
A brass screen will have leaf shapes cut out and given to the families of fallen officers, with the names of loved ones as a personal memorial.
Home Secretary Amber Rudd said the government had committed £1m towards the £4m needed for it.
"It is entirely fitting that those officers and staff who give their lives in the line of duty should be remembered with a lasting tribute," she said.
The memorial is expected to be completed by 2019.
An appeal has been launched for public donations towards a national memorial to police officers killed in the line of duty.