The base services the RAF's ageing VC10 tanker fleet
Nearly 340 jobs are set to be lost at a military aircraft maintenance base in south Wales, it has been revealed.
Defence Minister Quentin Davies told the Commons that the jobs would be lost at St Athan in the Vale of Glamorgan by June 2013 at the latest.
The closure, which will mark the end of a long history of defence maintenance, follows the end of a contract to maintain the ageing VC10 aircraft.
Mr Davies said 200 jobs could go in the next year with the rest by June 2013.
Mr Davies said the Ministry of Defence (MoD) has begun consultation with the unions on the proposals.
An MoD source said that while it is hoped the jobs could could be lost through voluntary redundancies, compulsory job losses could not be ruled out.
The consultation will last until 6 January, the MoD said.
Mr Davies told MPs other options for the future of the Large Aircraft Business Unit (Labu) at St Athan, which is operated by the Defence Support Group (DSG), were not viable.
The last major maintenance on the RAF's VC10 tanker fleet will be completed by next December and contract activity will decrease by 70%.
Minor maintenance will still be carried out until the St Athan facility closes, he added.
"Despite the best efforts of MoD and DSG management there is insufficient new work to sustain current staff numbers and maintain the viability of the business over the medium to long-term," Mr Davies said.
"MoD believes it is therefore critical to DSG's continued effectiveness and efficiency as a trading fund to reduce the Labu's capacity and capability in a phased manner commensurate with the unit's declining workload.
He said they has explored the possibilities of finding alternative uses for the capacity at St Athan, but none have materialised.
Mr Davies said although they continue to remain open to viable alternative suggestions, he believed it would be "irresponsible, and not in the interests of the workforce, to delay decisions any further".
He said the option of transferring staff to other DSG sites would be maximised.
Mr Davies also said the workforce had played a "pivotal role" in supporting the UK armed forces with the vital equipment needed on critical operations, both at home and overseas.
There are still RAF and Army personnel based at St Athan, including the Special Forces Support Group (SFSG) and No 4 School of Technical Training.
The 1,000 acre base has a history of repair and maintenance, alongside training, stretching back 70 years to the start of World War II.
In recent years, the base has depended on defence maintenance contracts.
DSG took over maintenance at the base from the Defence Aviation Repair Agency (Dara), which was formed by the amalgamation of RAF and naval repair agencies and had its headquarters in St Athan from 1999.
But in 2007, fast-jet maintenance was lost from the base, which once employed 2,000 workers.
Andrew Brookes, an aerospace analyst at the International Institute for Strategic Studies, said: "What's happened over 11 years is the air force along with the other services have been cut and cut, and when you cut all those aeroplanes, there is no longer the requirement for the skilled manpower to maintain them.
"When you start giving those servicing contracts to the lowest tender and those in industry, that means you start losing the valuable skills you have at St Athan and other places."
But plans for a £12bn defence college at St Athan, creating thousands of jobs, are still in the pipeline and Vale of Glamorgan MP John Smith called for the skills of the workforce to be retained to ensure its future success.
Mr Smith called on the new First Minister, who will be announced on Tuesday, and the MoD to work hand in hand to retain the skills of workers.
"As was shown in the National Audit Office's report in March of this year about the super hangar at St Athan, we don't want a repeat of the parlous state of affairs when one arm of government doesn't properly link up with devolved agencies to deliver on projects of national importance for the future of our armed forces," said Mr Smith.
Plaid Cymru spokesman Adam Price MP said the news came as a "dreadful shock".
He added: "These are good, skilled jobs which are being lost because the UK government has let down the people of Wales and there must be a duty on the Ministry of Defence to provide funding for re-training and re-skilling and not leave it again to the assembly government to pick up the tab."