Liverpool City Council is refusing to validate the application by Northern Irish practice Hamilton Architects for a £15 million three-storey building on the historic Pier Head until it has seen further details about the proposals.
It is understood the authority is particularly keen to see 'more supporting documentation relating to the conservation area aspects of the scheme'.
The original terminal plans were submitted in October just days after UNESCO's World Heritage inspectors left the city following an investigation into the potential impact of new developments on Liverpool's well-known waterfront ( 3XN astonished by surprise new Mersey neighbour).
The council is still waiting to get its hands on the official UNESCO report - which was due last week and is expected to set out its concerns about the raft of new developments springing up around the Three Graces.
Liverpool Preservation Trust chairman Wayne Colquhoun is hoping the latest decision to ask for more information signals a change within the city's planning department to stop 'the total annihilation of the World Heritage core'.
He said: 'Nobody wants the regeneration of Liverpool more than me, but this building is like sticking the worst piece of icing on the worst cake.
'It is a disgraceful design which looks more like something from Space 1999. As it says on the Unesco website, any new construction within the [World Heritage] site should be recessive not dominant.'
However, a spokesman for Merseytravel maintained the scheme was still on track. He said: 'We are continuing to aim for planning early in the New Year.
'We are still in discussions with Liverpool City Council and are supplying any additional information they need.'