AMs expressed disappointment on 2 March 2011, at the UK government's decision not to electrify the rail line as far as Swansea.
The UK government confirmed St. David's Day the £1 billion electrification of the Great Western line between London and Cardiff.
Economy and Transport Minister Ieuan Wyn Jones AM, whilst welcoming the announcement, was disappointed that the previous Labour government's opinion of the business case to electrify as far as Swansea had not been honoured.
Plaid Cymru AM Dai Lloyd said that there was a belief in Swansea that a negative perception of the city was the reason behind the decision.
Peter Black AM agreed that the decision sent a signal about business confidence in the city, but that there would be benefits in terms of inward investment.
Work on the line would begin in 2017, giving the assembly government a window of opportunity to convince the UK government to electrify the line as a whole, he added.
Mr Jones agreed, saying that he had urged the UK minister to reconsider and would work closely with his department to prove the business case for full electrification.
The Welsh Conservatives AM Darren Millar welcomed the decision and criticised the former Labour government for "not electrifying a single inch of railway" whilst in office.
The electrification will decrease the travel time between the two capital cities by 20 minutes and the trains will be cheaper to run.
Read this in Welsh.