Last week, Theresa May vowed on the steps of Downing Street to fight the “burning injustice” of inequality and to lead a government driven not by the interests of the privileged few, but by the needs of ordinary families.

Only time will tell if this is the ambitious vision of a leader who wants her legacy to be much more than the successful negotiation of Britain’s exit from the European Union.

In her words, there were some shades of continuity with David Cameron, who liberally deployed the rhetoric of fairness throughout his own tenure at Number 10.

But while Cameron borrowed from Blair, May’s pitch had an altogether different flavour: a greater emphasis on Blue Labour concerns of class and culture and on Miliband-style, long-term economic reform.

Will this rhetoric translate into action? Or will her government go the way of the Cameron-Osborne years, marked by symbolic policies designed to show off reformist credentials such as a higher national minimum wage and devolution to the northern cities, but which were more than offset by the damage caused by the government’s broader approach to economic and social policy?

A genuine commitment to the vision she set out will not, by itself, be enough: she faces the most difficult governing circumstances of any postwar prime minister.

The first clues about the type of government May will lead lie in her decisions about her cabinet. Most striking was her appointment of a series of leading Brexiters to the top outward-facing jobs.

In doing so, she has ensured some of her party’s most prominent backers of Leave will be involved not just in negotiating Britain’s terms of trade with the world post-Brexit, but in selling that deal to the country.

But it comes at a cost.

There is little to suggest David Davis, who, as the minister in charge of Brexit negotiations, now holds one of the most important jobs in government, understands just how difficult they will be.

His reading of how events will play out is naive: he wants to trigger article 50 by the beginning of next year and believes we should have trade deals with the rest of the world agreed within a year or two.

Boris Johnson’s elevation to the job of Britain’s top diplomat sends an unfortunate message to the world: that the job of foreign secretary is not one that our new prime minister takes seriously.

Why else appoint a man with a fondness for casually racist jokes? A man who fabricated anti-European tropes as a journalist and likened the woman likely to be the next president of the United States to “a sadistic nurse in a mental hospital”.

In 2002, he referred to Africans as “flag-waving piccaninnies”. And during the recent EU referendum campaign he likened the EU to the Third Reich.

Not to mention having being sacked for being “less than frank” (ie lying) with a previous Tory leader.

If being an insulting, juvenile, cavalier liar is what you want in your foreign secretary, then Boris Johnson is an excellent choice. Otherwise, it’s the most dispiriting part of the new cabinet that May chose to reward a narcissistic buffoon with the opportunity to represent Britain to the world.

As the former Swedish prime minister Carl Bildt said: “I wish it was a joke, but I fear it isn’t.”

It isn’t. He is.

This suggests that foreign policy lingers low on the list of May priorities and that, in the wake of Brexit, Britain will become increasingly shy of its wider international responsibilities.

More promisingly, May has appointed moderate reformers to key areas of domestic responsibility. But the real test will be the extent to which we will see a shift in direction on economic and social policy.

Will new chancellor Philip Hammond, who has a reputation as a deficit hawk, be able to oversee a loosening of fiscal policy and the big investment in infrastructure needed to try and ward off some of the Brexit headwinds?

If May is serious about easing the burden on working-class families, will she reverse Osborne’s tax-benefit cuts, which, even after his tax credit U-turn, hit low-income families with children the hardest?

If she wants to tackle burning injustice, will she address the drastic cuts made to further education budgets, while universities have enjoyed on average a 30% increase in per-undergraduate funding?

Will she stop the forced sale of council homes and divert inflationary demand-side subsidies such as help to buy towards building more homes instead?

These are the tests by which her government should be held to account.

In normal circumstances, that job falls first to the opposition. Yet in the last week, Labour has continued to slash away at itself to create self-inflicted wounds. It is failing on two significant levels. First, it shows absolutely no signs of confronting the existential question it faces which has seen its working-class base eroded as a result of decades of structural economic and cultural change.

Ukip is about to lay siege to large tracts of its northern heartlands and unless Labour finds a way of reconnecting to working-class communities that feel it no longer speaks for them then the spoils will fall to Ukip at the next election.

Second, the Labour party is failing in its duty of mounting an effective opposition – a role critical to a functioning of democracy.

And last week, it became painfully clear that it is failing on an even more fundamental basis.

The party is no longer even capable of providing a space for a respectful political discourse. Some of its MPs and elected officials are receiving death and rape threats, many from those who appear to be supporters of Jeremy Corbyn’s leadership.

Last week, the party took the unprecedented step of suspending constituency party meetings until after the leadership election so as to avoid the risk of intimidation and abuse at local level.

It is a grim state of affairs when one MP, Luciana Berger, received an email message saying: “You’re going to get it like Jo Cox did”; when party representatives detail the abuse and intimidation that they have been subjected to; when constituency staff have to contend with bricks being thrown through windows at their place of work.

Much of the abuse is aimed at female MPs and many Labour insiders cite a growing misogyny among some of those activists who are deploying social media to campaign on behalf of Corbyn.

The Labour leadership needs to be emphatic and persistent in denouncing this fetid, vile atmosphere that has emerged –coincidentally? – since they came to power 10 months ago.

Corbyn voted against a secret ballot for the vote by the party’s national executive committee on whether he would need to secure nominations from his parliamentary colleagues to go on the leadership ballot – despite female representatives on that committee pleading for a secret ballot for fear of further harassment.

No one emerges from this well.

Not Corbyn, who has lost the support of 80% of his parliamentary party. Nor his opponents in the Labour party who have failed to articulate a clear, compelling alternative or settle on a candidate who might reasonably be expected to at least offer some degree of leadership in a party that is now led by a small group of embattled men with no interest in winning elections.

Corbyn, the shadow chancellor, John McDonnell, and the director of strategy, Seumas Milne, and a variety of ultra-left entryists are exercised by an urge to create an extra-parliamentary social movement.

And that is fine – except that the Labour party is a parliamentary party. They should do the decent thing and let those who believe in parliamentary politics take up the reins while they engage in grassroots activism.

The Labour party is at a crossroads. It can choose the slow road to intellectual renewal and the political rebuilding of its electoral base so that it can be a force again in parliament.

That can only happen if it appeals to a far greater constituency than it does at present. And that will be a long, hard road.

Or it can choose a much easier option and restrict itself to a narrow set of slogans that allow it to bathe in self-indulgence while the rest of the country turns its back or, more likely, turns to Ukip, the Tories, the Lib Dems or the Greens.

This may be terrific for those activists who show disdain for actually winning elections, but will be less fun for that constituency of people who have historically relied on the party to work on its behalf in parliament.

As Momentum’s grip strengthens on the party, it loses more and more momentum in the country at large. That’s the choice for Labour.

There is no long-term guarantee for the party in this. The last 12 months have shown the ideas that might secure its future have not yet been developed and it is incumbent on some group or caucus to make this case.

Only time will tell if Theresa May’s government will go the way of David Cameron’s: a platform for warm words about tackling unfairness and inequality that disguised a harsh reality in which life got harder for many of Britain’s least affluent families.

But one thing is certain: without a functioning opposition, it’s easy to see what is the most likely outcome.