The proposal, for a train every hour on the hour, is to be tabled when the North South Ministerial Council next meets, in April.

Transport Minister Conor Murphy said the two companies made a presentation at the last north-south meeting in October.

"They made a case for improvements in frequency and speed for the Enterprise, which is after all a flagship service linking the two biggest cities on this island," he said.

"The problem is that the way the road is being improved, it may soon be quicker for people to drive from Belfast to Dublin than go on the train.

"We asked the companies to work on the proposals and come back to the next meeting, and I would be supportive of moves to improve the service."

The long-term aim of both companies is an hourly service, but this would mean significant investment in trackwork, signalling and rolling stock.

Mr Murphy said, however, that the increase in passenger traffic since Northern Ireland Railways introduced new trains showed that investment paid dividends.

He said the next stage as far as NIR was concerned was to introduce new trains on the Larne line, where services are operated by older units at present.

" I can understand the frustration of passengers on the Larne line but we have made an investment in the track and now hope that new trains will be in operation as soon as possible."

Now funding for new trains has been approved, NIR is going through a procurement process with the aim to have the rolling stock in operation by 2011.

Asked about the prospect of rail links to the province's airports, Mr Murphy said that while the issue was kept under review, there were no immediate plans for such a move.

He said the DRD continued to monitor the situation but said that to open a station at George Best Belfast City Airport would mean relocating the halt from Sydenham, which would inconvenience existing passengers.

Mr Murphy said private sector finance would help accelerate plans to create a dual carriageway road link from the M2 at Templepatrick to Belfast International Airport.