Kim Herforth Nielsen, of Danish practice 3XN, said he had not been consulted about the three-storey, £10 million scheme next to his Museum of Liverpool building on the historic Pier Head, and admitted that he was unimpressed with the design.
The terminal proposals, by Northern Irish practice Hamilton Architects, have been unveiled just days after UNESCO's World Heritage inspectors left the city.
Surprisingly, the scheme was not mentioned in the UNESCO team's initial report, which left questions hanging over the impact of developments, including 3XN's museum, on the city's World Heritage status.
Nielsen said: 'I have not seen this before and it does not look good at all. The city has had a lot of focus on the pier head as an event area. Now it will be filled up by a building not unlike the Chinese restaurant on the site today, which everybody wants to get away from.'
Speaking about the heritage issues, he added: 'I can not understand why there has been so much focus on [our] museum if this will just pass through.'
But MerseyTravel, which is backing the ferry terminal scheme, said it had been involved in lengthy discussions with World Heritage officers, Liverpool City Council and English Heritage during the building's design.
MerseyTravel chief executive Neil Scales said: 'Consultation with each of these agencies has been vital to the development of these plans, which will make a huge difference to what is on the site, offering much better facilities for ferry passengers and the hundreds of thousands of visitors every year.'