Business secretary Sajid Javid is to argue small and medium-sized businesses benefit from EU membership - amid rising tension between Remain and Leave on the economy.
Javid will cite new figures which show 1.2m small firms export to Europe or supply firms that export to Europe, demonstrating the importance of free trade with the bloc.
On a visit to Birmingham, he will argue a quarter of UK small businesses either export to Europe or supply firms that do export to Europe, disproving the common Vote Leave argument that only a very small number of British firms rely on trade with Europe.
"This shows yet again that Britain’s small businesses are stronger, safer and better off in Europe," Javid will say.
"If we leave the EU, small firms are on the front line and that's a gamble with people's livelihoods I'm not willing to take.
"Small businesses are the backbone of our economy. Let's not break that backbone with a leap into the dark."
However, the Federation of Small Business has said it will stay neutral in the EU debate. Louise Stewart of the group today told the BBC that more than anything, its members "really want more information".
Responding to Javid's planned speech, John Longworth, chair of the Vote Leave Business Council, said: "I agree with what Javid used to say about the EU - before he changed his mind for reasons we can only guess at. EU rules damage all British businesses, and smaller businesses in particular - and hold us back from trading freely with the rest of the world.
"These government figures are extremely questionable. The reality is that only six per cent of British firms export to the EU, but 100 per cent are caught up in red tape and costs from Brussels. If we Vote Leave and take back control of our economy, our businesses will thrive."
The focus on small firms by Javid came as the economic argument between the rival camps went up a gear.
Prime Minister David Cameron recently said Vote Leave had lost the economic argument, now forcing it to focus on immigration, while Britain Stronger in Europe today claimed Vote Leave had issued £111bn in spending commitments.
However, prominent leave campaigners Boris Johnson, Michael Gove and Gisela Stuart wrote in The Sun that leaving the EU would allow the UK to reduce tax on energy bills, which currently can't be scrapped because of EU rules.