Pro-European Conservatives have warned that a vote for Britain to leave the EU would be a "jump into a void".
Former minister Nick Herbert has launched a new Conservatives for Reform in Europe (CRE) group to make the case for Britain to stay in the union, reportedly with the support of the Prime Minister.
He warned that leaving the EU would put investment at risk, undermine policing and security, and jeopardise access to European markets.
Writing in The Sunday Telegraph, Mr Herbert outlined what he believes are the potential risks to the UK from leaving the EU.
Leaving without the first idea of what we might get instead would be to jump into a void. What matters most to the British people is their jobs and security, living standards and public services. Whatever our views about the EU, the key long-term challenges facing this this country - how to deliver health and social care with an ageing population, how to increase our competitiveness and productivity, how to deal with our debt and live within our means - would not suddenly be solved by leaving. >
At the same time, Education Secretary Nicky Morgan expressed concerns that young British people could find themselves "cut off from the world" if the forthcoming referendum resulted in a vote to leave the EU.
In an article for The Observer, Ms Morgan argued that opportunities for young people could be dramatically curtailed if Britain was to leave.
"I think all of us agree what we don't want Britain to be: anti-competitive with more laws made overseas and with people travelling here for the benefits on offer rather than to pay their way," she said.
"But we also don't want our children to inherit a Britain cut off from the world, where their prospects are limited and their opportunities end at our shores."
The latest interventions come just days after Leader of the Commons Chris Grayling - an avowed Eurosceptic - said it would be "disastrous" if Britain was to remain in the EU with its current terms of membership.