The MP had written to Huw Roberts, Pembrokeshire County Council's Director of Transport, to ask whether the county council would be holding a public inquiry since there were many objections to the present scheme.
Mr Roberts wrote back denying that the county council were required to hold a public inquiry.
However, Mr Ainger's reading of the relevant regulations is in direct contrast to Mr Roberts' interpretation.
In a further letter to Mr Roberts, the MP pointed out that the regulations state that a public inquiry shall be held if the effect of the proposals 'is to prohibit the loading or unloading of vehicles of any class in a road on any day of the week', and went on to ask the council why they don't think a public inquiry is required.
Richard Walker, chairman of TWTRA, commented: "Nick Ainger's intervention is very welcome and he has highlighted a crucial aspect of the Regulations.
"Our members, harbour users, Caldey users and local traders have many other objections, but this clear focus by Mr Ainger on a technical breach of the regulations could be a breakthrough.
"We are as keen as he is to learn of Huw Roberts' response, assuming he hasn't already left to take up his new job.
"Perhaps the council can also explain why the Tourist Board promotes Tenby as a sailing centre but for the most popular months and times, sailors will be denied access to the harbour to supply or transport their boats. This is not an experiment like last year this order is to be permanent."
Alistair Mackay, vice-chairman of TWTRA added: "If anyone's interested in how local democracy operates in Pembrokeshire and if you have a problem with the form of pedestrianisation that the county council intend to introduce and are still wondering how you are going to cope in July and August, there is a cabinet meeting on Monday where the pedestrianisation scheme will be discussed.
"It is at 10 am at County Hall in Haverfordwest and the public are welcome to listen but not to speak.
"Cabinet members may speak and listen, but not question another member's sphere of expertise, so you do have to have a mild interest in masochism to listen to people from everywhere in the county except Tenby discuss how we in Tenby are to be told to organise our lives. We are going."
"The next meeting of TWTRA, will be the first AGM and it will be held on 12 June, just before the scheme kicks in."