The North West Development Agency has agreed to pay £100,000 and English Heritage £20,000 towards the cost of the policy document that will tell developers what is permitted in areas within the heritage site zone.
The city council's executive board is set to meet to discuss the calls for better planning controls for the site, which takes in the Pier Head, Castle Street and historic areas of the city.
But Wayne Colquhoun, chairman of Liverpool Preservation Trust, told the Liverpool Daily Post that the Unesco document would be too late. He said: 'The damage has already been done to the critical areas of the WHS around Mann Island.'
In June (Conservationists attack decision not to list Liverpool) Colquhoun attacked Unesco's decision not to put Liverpool on its World Heritage 'in danger' list.
He said: 'The central core of the World Heritage Site is being eroded. The Three Graces at the pier head are being swamped by modern developments.