Business leaders from across Europe are to highlight the value of Britain's membership of the EU as the two sides in the referendum continue to slug it out over the economy.
Groups representing 3.3 million firms in Germany, France, Spain and the Netherlands will say that EU membership is the bedrock of their links with the UK.
The CBI said Britain's membership was an important factor in attracting £377 billion worth of investment in the UK from these four countries alone, with £185 billion of investment going the other way.
In contrast, Leave campaigners are to highlight claims that rising debt and pension costs in the eurozone will damage the British economy if it remains a member of the 28-nation bloc
Carolyn Fairbairn, CBI director general, said the scale of the investment between the UK and its leading EU partners underlined the importance of a Remain vote on June 23.
"European businesses are clear that 40 years' worth of collaboration through the EU is critical to attracting investment to the UK - let's not turn our back on our closest partners," she said.
"We must not put barriers in the way that could risk over £550 billion worth of investment between the UK and four major European economies alone, which supports jobs across the country."
Her warning is being echoed by the chief executive of the EEF manufacturers' organisation, Terry Scuoler, who will express concern at the "fevered and unpleasant" debate over the impact of EU migration.
In a speech in Brussels, he will say the UK economy is "heavily reliant" on migrant labour, with the EU nationals accounting for 10% of the workforce in the industrial sector "without whom it would not function".
"We are being assailed by a blizzard of often contradictory information dressed up as economic fact and the sometimes vile misinterpretation of issues concerning migration, security, and welfare as being linked to our membership of the EU," he will say.
"It is a fevered and unpleasant and at times quite farcical debate which I fear can only get worse as we approach June 23."
Meanwhile the chairman of the Vote Leave campaign, Labour MP Gisela Stuart, will say the eurozone economies are a "ticking time bomb" that will damage the UK if it stays in.
She will point to calculations by the pro-Brexit group that suggest rapidly rising pension and debt liabilities would require taxes to rise by at least 17.6% across the single currency group.
"This daunting demographic reality just goes to show that the eurozone is a ticking time bomb - an alarming reality that all EU members will inevitably be affected by," she will say.
"The priorities of the eurozone will gradually and inevitably take over Brussels institutions. If we don't want to be part of this we must vote 'leave'."
Vote Leave said projections of dramatic rises in the proportion of older people in the eurozone populations "raise significant questions about the long-term economic competitiveness of eurozone countries".
Combined with an excessively optimistic European Commission expectation that there would be no increase in public debts over the next 10 years, it said, that was a recipe for disaster.
The cost of public pension expenditure was estimated to rise by 2.1% of GDP between 2015 and 2050, from 12.1% to 14.2% and the cost of debt interest payments from 1.8% of GDP to 6.9% of GDP over the next 35 years, it said.
Plugging the gap could mean raising the total revenue collected from taxes by 17.6%, it suggested.