Britain’s record on social mobility leaves much to be desired. OECD figures show people’s earnings in the UK are more likely to reflect their parents' than in any other advanced country - with this relationship growing stronger, rather than weaker, over time. Furthermore, despite only 7 per cent of the population in the UK going to a private school, this group make up a staggering 32 per cent of MPs, 51 per cent of top medics, and 70 per cent of judges.

Recent events – in particular the Brexit vote – have added a new urgency to this agenda. In particular, the vote has highlighted the increasing geographical divide in the UK, and new analysis by IPPR, the UK’s progressive think tank, shows the link between the people’s ability to get on in life and their decision to vote leave: 97 per cent of the least socially mobile local authorities voted to leave the EU, compared with just 13 per cent of the most mobile regions.

The UK is increasingly divided between social mobility “hotspots”, which are overwhelmingly located in a small number of urban areas and their wealthy commuter belts, and “coldspots”, largely to be found in (often post-industrial) rural, costal and satellite towns. In places like Blackpool, Derby, Great Yarmouth, Middlesbrough and Doncaster, the reality for most is low paid and precarious work, poor housing, less effective schools and shorter lives.

There has always been a moral case for intervening to improve social mobility: Brits know that getting on in life is too often about who you know, not what you know, and the majority believe that this is unjust. Likewise, Boston Consultant Group recently made the economic case for change, estimating that poor social mobility will cost the UK economy up to £140 billion a year in wasted potential by 2050.

However, new evidence on the link between geographical inequalities and the Brexit vote – as well as similar trends in the US – demonstrate that there is also a political argument for increasing social mobility. If the benefits of the status quo are not felt, then people are prepared to rebel against it. There is a very real risk that, without significant improvements in daily life for the majority, people will opt out of the political system entirely, or reach for populist or anti-democratic leaders.

This insight has big implications for policy. The government is rightly focusing on the immediate priority of negotiating Britain’s exit from the EU, but unless it can also address the causes of Brexit – of which a lack of social mobility is a significant one – this effort may well be in vain. Theresa May seems to get this, arguing that her government’s mission is to make Britain a country that works for everyone: “I want Britain to be the world’s great meritocracy – a country where everyone has a fair chance to go as far as their talent and their hard work will allow.”

The question she now faces is what to do about such significant geographical inequalities. Historically, policy makers have let the free market drive growth in certain places and sectors of our economy – with people encouraged to move into areas of prosperity in order to improve their lot. A Policy Exchange report from 2008 took this argument to the extreme, suggesting that “places like Liverpool, Sunderland and Bradford were ‘beyond revival’ and residents should move south”.

The problem with this argument is threefold. Firstly, the data on internal migration shows that – for a variety of reasons, not least spiralling house prices in British cities – that it is rarely possible for those born in social mobility coldspots to move into mobility hotspots.

Secondly, even if we put policies in place to increase internal migration for these groups, all this would do is leave a smaller group of people in even more deprived areas.

And, finally, people have a profound connection with their hometowns, families and communities: they shouldn’t have to move away to make a decent living.

The evidence is now blindingly clear. Britain’s implicit social contract – that those who work hard will have a fair chance to get on – has been broken. However, the solution is not bussing people into urban areas, but sharing prosperity and opportunity across Britain’s rural, costal and satellite towns.

The government has made a promising start with Justine Greening’s Opportunity Areas policy, which provides extra funding for schools in social mobility coldspots. But in the future this will have to be expanded in to a much bolder and more comprehensive reform plan to really get to grips with the scale of Britain’s social mobility problem.

Harry Quilter-Pinner is a research fellow at IPPR.

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