Nicola Sturgeon has insisted it would be "unconscionable" for the UK Government to go back on its commitment to build vital Royal Navy vessels on the Clyde.
The SNP leader and First Minister spoke out as she met unions at the BAE Systems yards in Govan and Scotstoun to hear their concerns regarding the order to build new Type 26 frigates.
Ms Sturgeon visited the yard as Labour and the Liberal Democrats also insisted it would be a "betrayal" if Westminster altered the order for the 13 ships.
In the run-up to the referendum vote in 2014, pro-UK campaigners had insisted the work would not come to the Clyde yards if Scots voted for independence.
While Ms Sturgeon said it would be a "complete betrayal of these yards" if the order was scaled back or delayed, she refused to say if she would consider it a significant enough change in circumstances as to trigger a possible second referendum.
Fears were raised after it emerged in March the current demonstration phase of the project was being extended to "further mature the detailed design of the Type 26 ships and to manufacture key equipment for the first three ships".
BAE Systems said then the Ministry of Defence was still committed to buying eight of the advanced anti-submarine warfare ships.
GMB Scotland secretary Gary Smith said: ''We've gone from the upper Clyde workforce being promised the manufacture of 13 Type 26 frigates in 2014, for that to be cut to eight frigates last year.
''We've gone from promised investment that would secure thousands of skilled jobs and hundreds of apprenticeships for a generation, only to be told to prepare for redundancies.''
Speaking outside the Govan yard, Ms Sturgeon said: "Promises were made about orders to these yards and promises were made about jobs at these yards, and I think it is absolutely vital now these contracts are delivered.
"These yards have been through some really difficult times with a reduction in the workforce and they thought that that was all part of the process of getting themselves into shape for the Type 26 and securing a level of employment here.
"If there is anything happening that puts that at risk, I think that is unacceptable, so I want to listen directly to the unions about the concerns they have and then I will, as necessary. raise these with the UK Government.
"I think it would be unconscionable for the UK Government to go back on the promises that were made to these yards."
When asked if that would be considered a material change in circumstances from 2014 - one of the criteria the SNP says needs to be met before another vote on independence can take place - she stated: "This is about jobs and securing jobs in an industry. It would be a complete betrayal of these yards if there was any u-turn or going back on on promises made.
"That's why it's really important we make sure that doesn't happen and the first step in that is to hear directly from the unions, to understand what is making them so concerned."
Scottish Secretary David Mundell said: "The UK Government is absolutely committed to shipbuilding on the Clyde, and to the Type 26 programme, which is a very significant investment.
"Over the next decade we will spend around £8 billion on Royal Navy warships. We will also build two new offshore patrol vessels on the Clyde, maintaining Scottish shipbuilding capability ahead of the start of the Type 26 build.
"There will continue to be shipbuilding jobs on Clydeside for years to come and that is only because Scotland is part of the UK."
Scottish Labour leader Kezia Dugdale said: "We need to know that the Government remains committed to building at least 13 Type 26 frigates on the Clyde and that the promised upgrade of the facilities there will be carried through.
"If the Tory government delivers anything short of what they promised, then it will be a deep betrayal to the workers on the Clyde and their families."
Willie Rennie, leader of the Scottish Liberal Democrats, said: "There are serious concerns about the future of the orders at the yard and it's important that the Conservative government gives an absolute commitment to them.
"The Tories need to end the feast and famine of orders so the workforce can be maintained at a steady level."