Conservative right could limit Cameron's freedom to push reforms

Christian Odendahl, chief economist at the Centre for European Reform, a pro-EU think-tank, said Cameron could be more vulberable because he "cannot hide behind coalition politics any longer."

The Liberal Democrats had helped to "tame the more conservative, more Eurosceptic parts of his [Cameron‘s] party," Odendahl said.

"In addition, the Tories‘ overall majority will be very small, which makes the back-benchers more powerful, and could harden Cameron‘s stance," he said, adding that "internal pressure on the reform agenda, in particular on free movement issues, could increase."