A think tank estimates that more than 6,000 manufacturing jobs would be created in Wales by 2030 if Britain stays in the European Union.
The Centre for Economics and Business Research (Cebr) produced its report for Britain Stronger in Europe.
The campaign group has claimed the jobs would be at risk if the UK left the EU.
But Leave campaigners have called the findings absurd, claiming the jobs cannot be at risk if they do not exist yet.
The report has been published as manufacturers Airbus and Siemens, which both have major plants in Wales, are warning of the dangers of an exit.
They said that economic disruption and uncertainty that would accompany a leave vote would inevitably impact on long-term investment decisions.
Last year, Cebr produced a report estimating that if the UK stays in the EU and achieves the market reforms it wants, it could receive an economic boost worth nearly 3% of GDP, and 790,000 new jobs by 2030.
It has now published a breakdown of what it could mean across different parts of the UK.
It said 42,000 manufacturing jobs in Wales are either directly or indirectly linked to UK exports to the EU now. The report says this is projected to rise by 6,000 if there is a deepening of the single market.
In response, John Longworth, chair of the Vote Leave Business Council, said: "These daily threats are becoming absurd.
"The jobs they refer to don't even exist, so how can they be at risk?
"Instead of listening to speculation from advisory groups, let's look at what the job creators are actually telling us.
"Businesses up and down the country say that the costly red tape and regulations emanating from Brussels are constraining their ability to innovate and create jobs."