13/03/2015 13:32 GMT | Updated 13/05/2015 06:59 BST

More Women in Parliament - But There's a Hitch

It's over a hundred years since the first female MP was elected to Parliament. But sadly we're still a long way off equality.

Women currently make up less than a quarter of all MPs, at 22.8%. That puts us a miserable 56th in the world ranking for lower houses. Safe to say, we're not world leaders when it comes to female representation, sitting behind Afghanistan and Kyrgyzstan in the international league tables.

This election, though, could change that - to some extent at least. At the Electoral Reform Society we've used current polling trends, combined with lists of candidates for every seat in the UK, to predict how many women will be elected this May. The results are encouraging, but with one big caveat - our outdated voting system is holding women back.

On current trends, 192 women will be elected to Parliament in two months' time, making up 29.5% of the Commons. At almost 7% above the current level, it's a boost of the kind we haven't seen since female representation in Parliament doubled in 1997 to reach over 100 MPs for the first time. We'll be nearly double that again this time. So progress is being made.

There are some problems though. Firstly, not every party is moving at the same pace. Our analysis shows there are huge variations in terms of the percentage of candidates parties are putting forward who are women. The Greens top the league at 37%, but they are unlikely to make many gains. The SNP and Labour follow closely behind at 36% and 34% respectively, while Plaid Cymru (26%), the Liberal Democrats (25%), the Conservatives (25%) and UKIP (13%) trail behind.

But it's not just how many candidates you stand that matters - it's where you put them. Standing lots of female candidates is all well and good, but they need to be in winnable seats. For Labour and the Conservatives' marginal seats (their targets), 29% and 54% of their candidates respectively are women. This is an improvement on the current situation, and does mean something positive - women's representation is guaranteed to increase this May.

There's a hitch though. Our electoral system. Under the current First Past the Post system, there are hundreds of essentially uncontested seats, often held for decades by the same person. The longer the tenure, the more likely they are to be male, and the less likely they are to be unseated (owing to incumbency and the feeling that other parties can't win).

Of those elected ten years ago or before and re-standing this year, just 18.3% are women. And of those who were first elected in 1987 or before and are standing again this year, just 10.5% are female.

This raises a key problem for increasing women's representation in the future - what we've called 'seat blocking' by male MPs. First Past the Post, through its majoritarian nature and single-member constituencies, is the cause of this problem.

To open up those 'blocked seats' to competition from female candidates, we need to change our voting system. And while proportional representation isn't a silver bullet, it could facilitate a surge in female representation by opening up our political system to new parties and demographics who would finally stand a chance of winning against the 'traditional model' candidate.

So we need major reform to ensure May's increased representation of women doesn't become a new 'glass ceiling'. Reforming our archaic voting system, and encouraging wider citizen participation in parties and democracy more generally, could help ensure that the progress we are likely to see this May is not the end of the story.

Read the full report here