UP to 300 jobs are at risk in Chepstow following the announcement of a 'restructure' at engineering firm Mabey Bridge.
The company told employees that the infrastructure division, based near the town centre, will be closed and the renewables plant at Newhouse industrial estate will be put up for sale as a going concern.
The Mabey Group says the proposed changes will help build a "stronger, more sustainable future" for the modular bridge business which employs some 140 people at Lydney.
The company has now entered a consultation period with the 150 employees at Mabey Bridge.
Production should be maintained until May next year.
The renewables division – which is housed in a £38 million facility opened in 2011 – employs around 180 people.
In a statement issued last Thursday (December 11), a company spokesman said: "We regret to confirm that we have informed our employees today of the proposed closure of the Mabey Bridge infrastructure division at Chepstow. We also told employees that we have taken the very difficult decision to prepare the renewables division and the Newhouse site is for sale.
"We have not made these decisions lightly and we understand that this is a very difficult time for our people.
"Their welfare is an important concern for us and we will provide them with as much support as possible over the coming weeks.
"A full consultation process will now be conducted with all those affected and we will provide them with as much information as possible. We are also committed to listening to their views.
"Regarding the renewables division at the Newhouse site, we anticipate that a buyer can be found to provide the necessary investment to support this business in the long-term.
"Like many companies we are forced to consider every possible option to remain competitive in difficult times.
"The proposal follows a comprehensive review of the Mabey Bridge business.
"We are confident that these proposed changes will help build a stronger, more sustainable future for Mabey Bridge's modular bridge business in Lydney."
Monmouth MP David Davies met with Mabey executives on Friday to discuss the announcement.
He said: "This is a bolt out of the blue and is of great concern.
"I met with them two months ago and this was not mentioned."
The deputy leader of Monmouthshire County Council, Cllr Bob Greenland (Con, Devauden) and chief executive, Paul Matthews spent most of Friday morning with representatives of Mabey Holdings.
Cllr Greenland said: "The company provided a very honest assessment of their commercial position.
"While clearly being disappointed with the news we were reassured by the thoughtful approach that the board is taking and the absolute priority that they are attaching to their highly skilled and committed workforce in Chepstow.
"Through a combination of enhanced voluntary redundancy and redeployments within the group they are looking to mitigate the number of people who will be left without work.
"Very little change is anticipated before March 2015 to employee numbers and a number of existing orders extend production into May 2015 so there is some time, although not very much.
"We are pleased in their confidence levels for selling their state-of-the-art renewables business as a going concern which will clearly be good news as it will safeguard significant numbers of jobs.
"As a council we will be providing all the support that we can and will be using our networks to assist those seeking new jobs."