David Cameron is to set out what he sees as the benefits of the UK staying in the EU after claims he has focused too much on the risks of leaving.
The prime minister will say full access to the EU's internal market reduces trade barriers for British firms.
It comes as Prof Stephen Hawking and 150 other scientists warn that EU exit would be a disaster for UK science.
But Commons leader Chris Grayling will say the UK's sovereignty will continue to be diminished if it stays in the EU.
Mr Grayling, one of five cabinet ministers backing EU exit, will say Mr Cameron's renegotiation deal may leave the UK in a worse position than before, unable to veto future political integration in the EU.
'Calm and rational'
Voters will decide on 23 June whether the UK should remain a member of the EU or leave in a referendum that the prime minister will describe as "the most important decision for this country in a generation".