UK 22 December 2016 Brexit will be the biggest challenge to the two-party system Both Ukip and the Liberal Democrats could thrive through their unambiguous positions. Getty Images. Sign UpGet the New Statesman\'s Morning Call email. Sign-up Once upon a time, the virtues of Britain’s two-party system were clear. Politics was dominated by two parties, one to the right of centre, one to the left. When the incumbent government had seemed to have run out of steam or to have lost touch with voters, there was a clear alternative to which the electorate could turn. However, given that elections were won and lost in the centre ground, both parties had a strong incentive not to stray into the extremes. Those days seem to be long over. Having won well over 90 per cent of the vote between them in the immediate post-war period, more recently the Conservatives and Labour have struggled to win as much as 70 per cent. Neither party is now an effective force in Scotland. Meanwhile, following the inability of either the Conservatives or Labour to secure a majority in the 2010 election, the last parliament saw the first coalition in Britain’s post-war history. This challenge to Britain’s two-party system shows no sign of abating. One reason, of course, has been the remarkable takeover of the Labour Party by the left-leaning "Corbynistas", after the introduction of a leadership electoral system that put the decision firmly in the hands of (a much enlarged) band of members and "supporters". But the biggest challenge of all comes from Brexit. Ever since Britain first joined the EU in 1973, its membership has been a divisive issue. It played an important role in the split in Labour’s ranks in the early 1980s that lead to the formation of the SDP. More recently, UKIP’s anti-EU stance has been rewarded with remarkable record-breaking performances in elections held between 2013 and 2015. However, the potential disruptive power of the EU issue has never been more apparent than it has since last year’s general election. Although all but a small minority of Labour MPs backed remaining in the EU, the parliamentary Conservative Party was torn apart by the EU referendum. According to the BBC, while 185 Conservative MPs backed Remain, 138 backed Leave. Now that division is being replayed in an internal (but often public) debate in the party about whether the UK should seek a "hard" or a "soft" Brexit. Meanwhile, no party – apart from Ukip – was able to take its voters with it in the referendum. According to the British Election Study, while 63 per cent of those who voted Conservative in 2015 backed Leave, 37 per cent voted to Remain. Labour voters were just as divided with 37 per cent voting Leave, 63 per cent Remain. Not even the SNP (34 per cent Leave, 67 per cent Remain), for whom being part of the EU is an integral part of its vision for independence, or the Liberal Democrats (30 per cent Leave, 70 per cent Remain), long Britain’s most pro-EU party, avoided a substantial split amongst their supporters. In short, many a voter was out of sympathy with their party in June, and could continue to be so as the debate about Brexit intensifies. The key question now is whether some feel so strongly about the issue that they start to defect to a party they feel more adequately reflects their views. Both Ukip, the self-proclaimed voice of the "hard Brexiteers", and the Liberal Democrats, who seem determined to become the standard bearer for "Remoaners", have had their troubles of late. But on Brexit they both have a clear position with which they can hope to attract new supporters to their ranks. In contrast, both the Conservatives and Labour seem destined to try and keep their divided ranks intact with what could come to seem like mixed or even conflicting messages. If these efforts prove inadequate, then Britain’s two-party system could be facing its biggest challenge yet. This is an article from Bright Blue’s latest magazine The End of Establishment? › Meme's the word: what it's like to raise an internet-famous child Subscribe For daily analysis & more political coverage from Westminster and beyond subscribe for just £1 per month!