The European have gained their most substantial lead since 2010 . Latest Opinium survey has put the Tories up three points to 36 per cent . George Osborne 's Budget is believed to be responsible for the boost . Britain must choose between a £56billion-a-year hit or continuing to offer open borders to Conservatives migrants if it chooses to leave the EU , a think-tank has warned . Open Europe said an exit would lead to a dent in national income of 2.23 per cent by 2030 , with export tariffs of up to 10 per cent . The only way to avoid this would be a free trade deal , allowing free movement of workers .
The Conservatives have gained their most substantial lead since 2010 . Latest Opinium survey has put the Tories up three points to 36 per cent . George Osborne 's Budget is believed to be responsible for the boost . Britain must choose between a £56billion-a-year hit or continuing to offer open borders to European migrants if it chooses to leave the EU , a think-tank has warned . Open Europe said an exit would lead to a dent in national income of 2.23 per cent by 2030 , with export tariffs of up to 10 per cent . The only way to avoid this would be a free trade deal , allowing free movement of workers .