Economy minister Edwina Hart said the work will not stop to help find a buyer for the Murco site.
Her comments come as the Welsh and UK Government announced an agreement by Swiss-based Klesch Refinery Ltd to buy the site had collapsed, leaving hundreds of jobs at risk.
“This is a devastating blow to staff at the Murco refinery and companies within the refinery’s supply chain, as well as the local communities around Milford Haven. “Our support for the Murco refinery and its staff will not stop here. We have been working with management at Murco since 2010 to try to maximise the opportunities for the sale of the refinery.
“We will all continue to work tirelessly with Murco management to maximise the opportunities for employment at the site, ensure the ongoing viability of the terminal and assist to find a new owner.
The Welsh Secretary has expressed his disappointment at the news the deal to buy Milford Haven oil refinery Murco has collapsed.
Stephen Crabb took to Twitter to say he was 'desperately sorry' for Murco staff, whose jobs are now under threat yet again.
Incredibly disappointing news about Murco refinery tonight. Desperately sorry for workforce & their families - endured months of uncertainty
Grateful to UK & Welsh Govs for all their efforts to keep Murco refinery deal alive.The closure will be a huge blow to West Wales economy
Hundreds of jobs at the Murco refinery in Milford Haven are at risk tonight after a deal to buy the site collapsed.
Both the Welsh and UK Government has expressed its disappointment at the news.
400 jobs looked like they were safeguarded when Klesch Refining Ltd agreed a sale to buy the site back in the summer.
The deal was approved by the European Commission in October.
Wales Office minister Baroness Randerson said:
"This is extremely disappointing news for the workforce at Murco and their families.
“Supporting the staff at Murco is now our immediate concern and we stand ready to assist in any way we can."
Police investigating an alleged forgery in Milford Haven want to speak to this woman.
A £50 note was used to purchase low value items and change given. The note was later found to be forged.
Police believe the woman in the CCTV footage may be able to help with their investigations.
She is described as wearing a white top and black/white patterned trousers.
Anyone who can identify her or provide information is asked to contact PC Anthony Coleman at Milford Haven Police Station on 101.
Around 400 jobs have been saved after an agreement over the sale of the Murco oil refinery in Milford Haven.
The deal has been welcomed by Pembrokeshire Council, who have described the sale as 'good news' for Pembrokeshire and Wales.
The news has also been welcomed by the Minister for Economy, Science and Transport. In a statement today, Edwina Hart AM said: "Today’s announcement is very good news and the first step in securing the long-term future of the Milford Haven refinery."
The Secretary of State for Wales has welcomed the news that a deal has been reached over the future of the Murco oil refinery in Milford Haven.
On twitter, the Wales Minister described the deal between Murco Petroleum Ltd and Klesch Refining Ltd as 'excellent news' for Murco employees.
He added that it is "important to maintain UK oil refining".
It has been confirmed that a sale has been agreed on the Murco oil refinery in Milford Haven.
A deal has been agreed with Klesch Refining Ltd, and is expected to close no later than October.
Murphy Oil is pleased to announce that a deal has been agreed for the sale of the Milford Haven Refinery. We have worked tirelessly to find a workable solution that would see the refinery remain open, and are delighted that a positive outcome has been reached.
There are reports that an agreement has been reached over the sale of the Murco oil refinery in Milford Haven.
Hundreds of jobs were under threat when a deal to save the site collapsed in April.
News agency Reuters are this morning reporting that The Klesch Group have agreed to the buy the refinery.
ITV News understands than an announcement over the future of the refinery is due later today.
Hundreds of jobs at the Murco Oil refinery plant in Milford Haven could be saved, if a deal to sell the site goes ahead. The local MP Stephen Crabb says that an agreement has been reached in principle - which would end the current uncertainty. Nicola Hendy reports.
Commenting on the potential sale of the site a Welsh Government Spokesman said **
The plant is a vital part of the Welsh economy and we have been working tirelessly to secure its future, working closely with the current owners, potential buyers and government at all levels. “We remain committed to exploring every possible angle in supporting the company and the workforce.