Frances O'Grady
Frances O'Grady, the general secretary of the TUC, will challenge Theresa May to make sure all industries enjoy the advantages of access to the EU's single market Getty

The tens of millions of workers across the UK should not have to pay the price for Britain's decision to split from the EU, Frances O'Grady will warn today (12 September). The Trades Union Congress (TUC) chief will challenge Theresa May to keep her social justice pledge and "step in" to make sure all industries enjoy the advantages of access to the EU's single market.

"Whether you voted Leave or Remain, now the vote is over our job is to get the best deal possible for working people," the general secretary is expected to say.

"We must build a Britain that is successful, prosperous and fair – a Britain of great jobs for everyone.

"Government must be ready to step in and work to keep the advantages we get from membership of the single market – for all of our industries, not just the City. That's the key to a successful Brexit for working people."

O'Grady's warning will make up part of her keynote address to the 2016 Trades Union Congress in Brighton.

Len McCluskey, the general secretary of Unite, said the Remain campaign lost the EU referendum because voters wanted to give the establishment a "kicking".

"Far too much of Britain has been left behind by globalisation. Whole industries have disappeared, leaving communities derelict and generations without hope," told delegates on Sunday 11 September, the first day of the conference.

"Add to that austerity and cuts in services on top, with relentless downward pressure on wages; and an elite that has passed the burdens of the crisis onto the less fortunate – and it is not surprising that millions of people, including significant numbers of our members, voted to give the establishment a kicking."

Major trade unions, including Unite, Unison and the TUC, campaigned for Remain alongside Labour and Jeremy Corbyn at the referendum, while the RMT, train drivers' union Aslef and the Bakers' Union backed a Leave vote.

The TUC welcomed Brexit Secretary David Davis' announcement to MPs in early September that he would lead a national, inclusive consultation on which model the government adopts to split from the EU.

May has ruled out triggering Article 50 of the Lisbon Treaty, the official mechanism to break away from Brussels, this year. The government is expected to make the move in 2017, meaning the UK would split from the EU in 2019 after two years of negotiations.

O'Grady addresses the referendum result:

The referendum result on Britain's membership of the European Union heralds a whole new era of uncertainty for the working people we represent.

The General Council asked me to lead a campaign that talked about what was in the best interests of working people. About the rights we enjoy - fought for by unions but guaranteed by the EU. About the risks to our economy and our public services – our precious NHS. And about what life outside the single market could mean for jobs.

The campaign wasn't easy.

For me personally, facing Boris and Andrea Leadsom in the BBC debate was quite an experience. And not one I'd be in a hurry to repeat. But, as someone told me, at least now I can say I've played Wembley.

The campaign wasn't clean, or even honest. Fake promises of more money for the NHS. Dog whistle appeals to anti-immigrant sentiment. And the bizarre spectacle of a self-styled anti-Establishment vanguard.

Led by a serial back-stabber, a former stockbroker and a member of the Bullingdon Club.

While many sat it out, we stepped up. We made sure our members knew what we thought. And, in the end, our polls showed that a majority of trade unionists voted Remain.

For many it wasn't an easy decision. And I respect those who thought differently. Especially those in our movement, who made the judgement they thought best. And those in the communities we have always championed. Who paid a high price for globalisation, And are still paying the price of the crash.

In this movement, we're democrats. We accept what the British people have said.

So I say this: Whether you voted Remain or Leave; our job now is to get the best deal possible for working people. And to build a Britain that is successful, prosperous, fair. A Britain of great jobs for everyone.

We face a new government and a new prime minister too. Now, as a rule, I'm all in favour of having more women in charge. But it's no secret that this isn't one I would have chosen.

Nevertheless, in three weeks' time she will be stood in a hall like this one. Giving her big speech to an audience that's... well, a little different from this one. And, woman to woman, I'm going to take the liberty of giving some advice about what she should say.

After all, on the steps of Downing Street, the new prime minister admitted that life is much harder for working people than many in Westminster realise.

She promised us social justice. She vowed to govern for the many, not the privileged few. So my advice to the new prime minister is this: prove it. Show us that your top priority is to make sure workers don't pay the price of Brexit.

There are five tests that must be met before you pull the trigger on Article 50.

First: EU citizens living and working in the UK must be guaranteed the right to remain. They are our friends, our neighbours, our workmates. It is plain immoral and inhuman to keep them in limbo. The public agrees: guarantee their right to stay.

Second: we need an all-Ireland agreement on economic and border issues. This movement worked hard for jobs, justice and peace. It would be foolish to take that for granted.

Third: we keep being told that Brexit means Brexit. I'm not sure many union leaders would get away with saying a walk-out means a walk-out. A strike means a strike. And that's that.

At some point we'd have to spell out what we want. What we think we can get. And win a mandate from our members to negotiate. The same goes for the prime minister.

How can her government know what to negotiate for if it doesn't know what the country thinks?

Or what the rest of the EU would accept?

Now in some corners of Whitehall there is talk about Canada and the CETA [Comprehensive Economic and Trade Agreement] model.

Well, let me give the government fair warning. Britain didn't vote for new trade agreements that: destroy jobs, set up secret courts and open the way to privatisation. If they go for the son of CETA, we will make opposition to TTIP [Transatlantic Trade and Investment Partnership] look like a tea party.

The fourth point. Negotiating our exit can't be left to the Tories. This shouldn't be about managing the internal politics of the Conservative Party. It's about shaping the future of our country. We need a cross-party negotiating team, including the nations, London and the North. And it can't be a case of cosy chats with the City and the CBI either. As the voice of working people, trade unions must be at the table too.

And that leads me on to the fifth and most important point. Before we go for Article 50, we need proof that workers' rights will be safe. We fought hard for those rights. They weren't gifted by Brussels, but won by trade unionists. And people didn't vote Leave to get rid of holiday pay; to lose time off to care for sick children; or junk rights for temporary and agency workers.

And our European neighbours won't agree good access to the single market if Britain undercuts them as an offshore haven for cheap labour.

So, prime minister, no ifs, no buts. Guarantee workers' rights, now. And for the future. And tell us about your plan for the economy.

Just one week after the vote, the TUC published a national action plan. To protect jobs. To protect investment. To make sure ordinary working people don't pay the price. They can't afford it. After all, workers in the UK have already suffered the biggest fall in wages since the crash of any developed economy, except Greece.

Now, you won't catch me talking down industry. We know the importance of confidence. But, delegates, we remember the recession after the financial crash. We know, all too well, the risk of complacency too. And union reps across the country. Convenors at our biggest workplaces. They are telling me about the worry and uncertainty their people are facing.

Investment plans stalled. Job hires on hold. That means government must be ready to step in. And work to keep the advantages we get from membership of the single market. For all of our industries – not just the City.

That's the key to a successful Brexit for working people.