Translink state that they are 'currently reviewing' Enterprise rail fares between Northern Ireland and the Republic of Ireland

The Enterprise service is currently jointly run by Translink and Irish Rail.

However, the prices of your journey can be vastly different, depending whether your journey starts in Northern Ireland or the Republic of Ireland.

For example, if you buy a ticket to travel from Belfast Lanyon Place to Dublin Connolly Station on July 5 at 8.00am, it will cost an adult £33 for a one-way trip, or £48 for an adult to travel first-class.

On the other hand, if you were travel in the opposite direction on the same day - leaving Dublin Connolly Station at 7.35am - it would cost an adult (flexible) €15.99 (£13.50).

Currently, customers can only book tickets for the Enterprise on the website in the country where your journey stars from.

In addition, passengers from Northern Ireland cannot reserve a seat with standard or websaver fares.

A Translink spokesperson said: “The Enterprise service is operated jointly by Translink and Irish Rail.

“Each company has its own ticketing/IT systems, fare structures and special offers.

“Each fare structure is also designed to operate in conjunction with each operator’s local network.

“Both companies are subsidised in different ways and to different levels. We always encourage our passengers to review their best fare option online.

“We are currently reviewing Enterprise fare structures with Irish Rail”.

In an interview on BBC Radio Ulster’s Evening Extra programme last month, Andrew McDonald, an independent rail campaigner, does not believe there is any justification for the gap in prices.

He said: “I know Translink and Irish Rail do work together when it comes to their cross-border services, but it feels like when it comes to the actual pricing and ticketing structure, they just do their own thing.

“Maybe a bit more communication about how to meet in the middle with ticket prices, might be more beneficial.

“Maybe there is a strategy behind it we are not aware of, but if there is a strategy behind it, it would be nice to know why, because at the end of the day, it’s us the people that use the services that do suffer.”