In recent weeks, something odd has happened in British politics — something that has the potential to significantly transform the way the country relates to the European Union in the years to come. And yet, nobody seems to have noticed it: or if they have, to have not quite thought through the implications.

The ‘something’ in question is the prospect of electoral reform, now being considered by each of the two main parties as a condition for entering a coalition with the Liberal Democrats, who have recently surged ahead in the polls.

Why would this affect Britain’s role in Europe? I can see two possible outcomes, depending on whether the British adopt the alternative vote or shift to some form of proportional representation.

Switching to an alternative vote system, in which voters rank candidates from most to least favourite, could lead to a  Liberal Democrat ‘power broker’ scenario that will substantially moderate the likelihood of eurosceptic policies coming to pass. The reason is that alternative vote systems tend to favour centrist parties – such as the Liberal Democrats – as these are the ‘least repugnant’ (hence second-preference) option for most voters. With the Liberal Democrats as permanent kingmaker to either Conservative or Labour governments, both parties (in particular the Conservatives) would have to tread more carefully over Europe once in government, so as not to alienate the pro-European instincts of their new partner.

Moving to a proportional representation system, on the other hand, could send Britain deeper into the twilight zone than is commonly thought. Proportional systems favour fringe parties and extremists, who suddenly face no obstacle to parliamentary representation; groups such as the UK Independence Party, or even the British National Party, would almost certainly make inroads to Westminster – much as they have done in the European Parliament, where a proportional system is already used. While centrist coalitions might emerge at first, in the event of PR, could one forever rule out the possibility of some kind of purple-blue coalition (between the UK Independence Party and the Conservatives) that would seek to push through a fundamental renegotiation of Britain’s role in the European Union?