Murco has denied rumours the refinery will close and says it is working with a potential buyer who wants to run the site as a business.
Opponents say that offshore power and Wylfa Newydd's power could instead be piped under the sea - the most costly option.
With exactly half the seats in the Assembly, Labour needs at least one of the other parties to support its budget or abstain.
Preseli Pembrokeshire MP Stephen Crabb has described the news that a deal to sell the Murco refinery has fallen through as "a hammer blow" for the local area and the wider economy.
He said "hundreds of skilled, high quality jobs are now at risk", and called on the UK and Welsh governments to work together "to offer every possible support to avoid the worst outcome of full refinery closure."
The collapse of the Murco refinery sale is a hammer blow for Pembrokeshire and the wider West Wales economy. Hundreds of skilled, high quality jobs in our community are now at risk. Pembrokeshire has seen refinery closures before and we know the short-term impact can be colossal.
If Murphy Oil cannot do the deal with Greybull then it must explore all possible alternative sale options as a matter of urgency. I have met with one other buyer on two occasions now who so far has been locked out of the sale process because of the exclusive negotiations with Greybull.
I have had an urgent meeting with the Energy Minister Michael Fallon, and have asked that he and his department work closely now with Welsh Government to offer every possible support to avoid the worst outcome of full refinery closure. Everyone understands the seriousness of the situation and what this means for Pembrokeshire.
– Stephen Crabb, Preseli Pembrokeshire MP
The staff and management at Murco in Milford Haven have worked incredibly hard over the last three years to turn the plant around and create one of the leanest and most efficient refineries in the country. Their commitment and effort has been hugely impressive and it is a very sad day for them and their families to be told that the sale has collapsed.
Around 400 jobs at the Murco oil refinery in Milford Haven are at risk as the plant may have to close, after talks over selling it have collapsed.
Murco has announced it is today entering a period of consultation with staff, but says "it is not possible to predict the outcome of this process" at the moment.
The refinery has been up for sale for around three years, with talks though to be at an advanced stage with private equity fund Greybull Capital.
Today, Murco said: "Following the expiration of exclusive talks with a potential buyer, [parent company] Murphy and the company plan to speak with a small number of interested parties, which may or may not lead to allowing the refinery to continue to operate."
Watch our report from February: Fears for future of Milford Haven refinery
Sixty new jobs are being created in Port Talbot, by manufacturers Freundenberg Oil & Gas Technologies.
The German company is investing £11m to turn its three sites in Baglan into one larger base, with staff numbers rising from 237 to 297.
The Welsh Government provided £3m in support, says the decision will also safeguard around 90 jobs, and shows the company's commitment to Wales.
A compensation offer has been made to former workers at the Visteon car parts business in Swansea, whose pensions were affected when the company went into administration.
The settlement, thought to be worth millions of pounds, was agreed between the Unite union and Ford, who owned the business before selling it ten years ago.
Former workers were in London today to hear the news.
Tom Sheldrick reports.
A row has broken out over the future of Wrexham's historic markets.
Plans have been unveiled to replace some market stalls with a new cultural centre, plus bars and restaurants.
As the council starts to talk through the scheme this evening, the traders say things should be left as they are.
Rob Shelley reports.
The Unite union described its talks with Ford as "lengthy but constructive".
Unite has concluded an agreement with Ford to make a settlement offer to eligible ex-Visteon employees who filed legal claims in connection with reductions in their pensions resulting from Visteon UK being put into administration in 2009.
The settlement would avoid further expense for participants in the case and will settle the legal claims that these individuals have made against Ford.
Details of the settlement are confidential and a private matter for those directly involved.
A settlement has been reached to offer compensation to former workers at Visteon, five years after the car parts company went into administration, hitting employees' pensions.
Unite said it had concluded an agreement with Ford, which sold off the car parts business to Visteon over a decade ago.
It is understood that around 1,200 ex-workers from factories in Swansea, Basildon, Essex, Enfield in north London and Belfast will be covered by the settlement.
Ken Skates, the Deputy Minister for Skills and Technology, has hailed £2.3m of funding for training in the energy sector as "fantastic news."
The funding will focus on preparing people for work on major developments on Anglesey, especially Wylfa Newydd, the planned nuclear power station.
I’m delighted to announce this additional £2.3 million of funding from the Welsh Government to support the Energy Island Programme.This is fantastic news for Anglesey and the surrounding region.
A project as ambitious and wide-ranging as this will require a highly skilled workforce with the experience, knowledge and expertise to meet the demands of the energy industry, particularly when it comes to both the construction and operation of Wylfa Newydd.
– Ken Skates AM, Deputy Minister for Skills and Technology
This investment means that Grwp Llandrillo Menai can both expand its training provision and build on its links with industry to deliver the kind of practical, hands-on work placements that learners will need.
I’m also particularly pleased that, thanks to this funding, apprentices will be at the forefront of Energy Island’s development. Having work-ready young people in place to support major projects will make such a difference and, in the long-term, can only strengthen the region’s labour pool.
The Deputy Minister for Skills and Technology, Ken Skates, has announced a £2.3m investment in training for Wales’ energy sector.
This will focus on preparing people for work on major developments on Anglesey, especially Wylfa Newydd, the planned nuclear power station.
The boost was announced at a crucial meeting with Grwp Llandrillo Menai leaders at the Coleg Menai Energy Centre at Llangefni.
The centre is set to be the hub for programmes for a huge range of engineering, construction and support activities.
The investment will also be a major boost for apprenticeships, to ensure work-ready people are available as major projects build momentum. The Grwp has already established a successful apprenticeship employment agency, Cwmni Prentis Menai, and plans to build on its initial success.
The owner of SWALEC, SSE, is to freeze household gas and electricity prices.
The group is also carrying out a "legal separation" of its wholesale arm - which includes energy production and storage - from its retail division which sells energy to homes and businesses.
The announcements come as SSE says it's shedding 500 jobs as part of a cost-cutting programme.