Image caption BAE Systems' Govan shipyard will not be closed, BBC political editor Nick Robinson understands

BAE Systems is to cut potentially more than 1,000 jobs from three of its UK shipyards at Govan and Scotstoun in Glasgow and at Portsmouth.

The BBC has learned that major job losses at the yards will be announced by the company later this week.

Some of the jobs being lost may be offset by a contract to build the new Type 26 Global Combat Ship.

BAE Systems, however, has yet to announce which of its UK shipyards will be chosen to carry out the work.

BBC Political Editor Nick Robinson said the announcement by BAE Systems is expected on Thursday morning and will be followed later that day by a Commons statement from the defence secretary.

A well-placed source told me that the government was "acutely conscious of the politics of the Clyde" ahead of next year's Scottish Independence referendum

He understands that BAE's Govan shipyard will not close despite the fact that the possibility has been discussed behind the scenes in recent weeks.

He said a well-placed source had told him that the UK government was "acutely conscious of the politics of the Clyde" ahead of next year's referendum on Scottish independence.

The job losses, he said, would result from the completion of work on the building of two new aircraft carriers and from a huge increase in the costs of that project.

It emerged on Monday that the UK government is planning to announce that it will need to spend an extra £800m on the carriers, taking the total costs to more than £6bn - double the original estimate.

Beyond the carriers there are currently no new orders on the books of the BAE's Glasgow yards at Govan and Scotstoun.

Any job losses, however, may not take effect immediately because some work on the aircraft carriers is planned until 2015.

'Significant tension'

There are currently 3,200 people employed by BAE across Govan and Scotstoun, and 1,200 employed in shipbuilding at Portsmouth.

BAE launched a review of its defence work 18 months ago.

Media playback is unsupported on your device Media caption Scotland Secretary Alistair Carmichael: ''We will know in the fullness of time what the position is''

A BAE spokeswoman said: "We continue to work closely with the Ministry of Defence to explore all possible options to determine how best to sustain the capability to deliver complex warships in the UK in the future.

"This work is ongoing and we are committed to keeping our employees and trade unions informed as it progresses."

The Confederation of Shipbuilding and Engineering Unions said it would hold talks with senior BAE systems executives early next week to "examine the business case" of the forthcoming announcement on jobs.

General Secretary Hugh Scullion said: "Now is not the time for idle speculation or indeed party political point scoring, this is the future of an industry and we need to know from the company and the government directly what their plans for the future of UK shipbuilding are.

"The shipbuilding workforce throughout the UK are working flat out to deliver the aircraft carriers for the defence of the UK and they need to know what lies in store for them, their families and their communities."

'Question marks'

Scotland's Deputy First Minister Nicola Sturgeon said the workforce at both the Govan and the Scotstoun yards in Glasgow deserved to know what the future holds.

At the scene The sodden skies above the Clyde are bright tonight, lit up by splashes of red, white and green. But there are no celebrations to match the fireworks. The skilled shipbuilders of Scotstoun and Govan know better than anyone that they are only as good as their order book. They know too that the book is blank after 2015. So the mood beneath the cranes is mixed. Some workers are optimistic, hopeful that the Type 26 Global Combat Ship will keep them in work. Others fear the worst, suggesting that the company would rather move work to the south west of England. One even told me he thought Govan should be shut and the company's efforts focused on Scotstoun. But most, pouring out of the yards this afternoon, simply wanted information. They may have played this waiting game before but that doesn't make it any easier.

"Scotland is a maritime nation. If you look at countries similar to Scotland, like Norway, they have got much bigger shipbuilding industries than we do so there's no reason why both of these yards shouldn't have a secure, long-term future," she said.

"This is a very worrying time. Any talk of perhaps hundreds of job losses is of real concern to the people employed in these yards and right now the most important thing is for them to be given clarity."

The shadow defence minister called on the government for "urgent clarification" on the future of the UK's shipyards.

Vernon Coaker said: "What many people will want across the shipyards mentioned is some clarity and certainty about what actually is being proposed.

"It is important the government and BAE Systems come forward with what are the facts as soon as possible.

"There are thousands of workers and families wondering what their future holds."

He said it was important that the UK maintained the "skills and capacity" to continue shipbuilding, which is "important for (the) defence of our country".

Mr Coaker said BAE and the unions involved "work very closely" and "have a good relationship", and will be working together to ensure the UK maintains a ship building industry.

He also dismissed accusations that Labour was responsible for the overspend incurred in building the two aircraft carriers.

Gerald Vernon-Jackson, leader of Portsmouth City Council, said the council would "work as hard as we can" to save jobs at the Portsmouth shipyard.

Media playback is unsupported on your device Media caption Govan workers: "We don't know what will happen"

He said there were "question marks" over the yard and its future was a "strategic decision" for the defence of the UK.

"If all the British warship manufacturing is in Scotland, what happens in less than a year if Scotland is independent?" he said.

Scottish Finance Secretary John Swinney said the Scottish government had "been in dialogue for some time" with BAE Systems on the issues surrounding the future of the Clyde shipyards.

Scottish Secretary Alastair Carmichael said it was "no secret" that BAE was carrying out a review of its defence work but he warned against speculation.

"It is absolutely no secret that there is a review ongoing," he said.

"And it is quite possible that there will be an early conclusion to that but unless, and until, we are dealing in facts rather than speculation then for the people whose jobs are concerned then there is no usefulness in this at all."

'Vital jobs'

Scottish Labour leader Johann Lamont, whose Glasgow Pollok constituency includes the Govan yard, said: "Everything must be done to ensure shipbuilding on the Clyde continues.

"The UK government is the Clyde's biggest customer and I will be seeking urgent talks to make sure that continues.

"This will be a particularly worrying time for the workforce and their families but I will work with anyone to make sure we can keep these jobs.

"It's times like these that we all need to come together, put differences aside and fight to secure these vital jobs."

Scottish Conservative leader Ruth Davidson, who is a Glasgow MSP, said: "The current speculation over shipyard jobs is unhelpful and destabilising to both the workforce and their families.

"BAE's shipbuilders on the Clyde are a highly professional, motivated and loyal workforce and they deserve clear answers from the company about their future."