Concern is growing that Dublin Bus is on the road to privatisation after buses were spotted around the city with a new paint scheme.
The livery will be fully introduced once a new operator starts running on 24 routes across the capital later this year - but the new look does not include the distinctive Dublin Bus branding.
Instead the buses carry 'Transport for Ireland' logos and new colours.
Fianna Fail TD John Lahart said he was concerned this was part of a phasing out of the Dublin Bus brand, which would make it easier to bring in privatisation across the fleet.
A new blue scheme with flashings of green and white will be adopted on buses used by private operator Go Ahead when it starts running on the 24 routes this autumn.
Under the terms of the Dublin Transport Authority Act, the National Transport Authority (NTA) has the powers to implement a single brand and colour scheme to be used by all transport operators in the capital.
The NTA said these colours would be used on new Dublin Bus vehicles from next year and the distinctive yellow markings currently in operation would gradually be phased out as older buses are replaced.
New livery for Dublin Buses - quieter than the yellow. I hope they are going to brand Dublin Bus and Go-Ahead in the same colours so that it all looks like the same service to the passengers.— Cllr Ossian Smyth (@smytho) April 3, 2018
(photo by Mark Newman) pic.twitter.com/7uBrJwNgVY
Mr Lahart said he would like to see this decision reversed.
"Dublin Bus is part of the fabric of Dublin and I don't think it should be eviscerated so easily," he added.
"Feedback shows the colours appeal to people with special needs and are a help to people who are visually impaired -they can see it coming and the current scheme was chosen with this in mind.
"I think the Dublin Bus brand is worth defending and fighting for.
The new Go Ahead buses will not carry the Dublin Bus branding but instead the NTA's 'Transport for Ireland' logo and the company's own name.
Mr Lahart is concerned this could lead to the privatisation of the capital's bus network.
"If the public get used to a universal livery then it is very easy to bring in private competition and the public doesn't really know anything about it," he said.
"I think it would promote competition and efficiencies across the system if it was easy to identify service providers.
"They would be easily compared and people would know what services they are using."
A spokesman for Dublin Bus said the company's brand should be maximised.
“The Dublin Bus brand is an iconic brand, which is widely recognised nationally and is a significant asset to the state. The value of this citizen brand should be utilised to the maximum, building on its strong performance to drive further customer growth. Dublin Bus will continue to work with the NTA to seek the best possible outcome for our customers, company and city.”
The NTA said it had no plans to privatise the fleet.