Listening to Theresa May's statement on triggering Article 50, I was surprised by how much of it sounded like something I might say as co-leader of the Green Party.

She said she wants a "stronger, fairer Britain". She called for a society which is more outward-looking, secure, prosperous, and tolerant. And I also want to shape a Britain which our children and grandchildren are proud to call home. That all sounds good.

The thing I can't get my head around, though, is how our prime minister thinks any of this will be achieved by the extreme Brexit she's driving us towards. The truth is in the reality, not the rhetoric.

We are looking at a bonfire of workers' and environmental protections. Boris Johnson, a government minister, is already applauding the Telegraph's Brexit campaign "to cut EU red tape".

Our economy and public services are further endangered by restricting migration and cuts to corporation tax, and we risk a reduced role in a world facing challenges which need stronger and stronger international collaboration.

And no matter how much bluster she puts on, this was not on the ballot paper.

Throughout her statement, May kept referring to carrying out the will of the people, as if what we're seeing today is a triumph of democracy. First of all, it's worth making the simple but important point that only a slim majority of the country voted to Leave, and these people did so for a huge range of reasons.

That slim majority has been morphed into a mandate for an extreme Brexit by a government hell bent on using this moment to reshape Britain in their benefit. It's a stitch up by Tories pandering to Ukip.

If our prime minister is sincere in her desire to reflect the wishes of the people, then she should treat the 2016 referendum as the beginning of a democratic process, not the end of one. This hasn't looked promising so far. The government had to be taken to court just to get a vote on triggering Article 50 in the House of Commons, and we're going to have to pile pressure on the government to get a vote on the terms of the deal in two years' time as well.

Of course, the things May didn't say are just as important as the things that she did. And neither the letter to Donald Tusk nor her statement in the Commons mentioned the environment.

Protection and improvement of our environment is one of the greatest success stories of UK membership of the European Union (EU). When we joined, our beaches were filthy and we had the odd downpour of acid rain. But with EU support, we've cleaned it up, while also playing our part in tackling the international crisis of climate change.

Coming out of the EU puts all of this at risk, and I don't trust it in the hands of Theresa May's government. She at least paid lip service to the protection of workers' rights, but the fact she didn't even bother to mention our air, water, soil or climate shows us how hard we're going to have to fight to protect the advances we've made in recent decades.

In fact, from climate change to the refugee crisis to tax avoidance, a great number of today's most pressing challenges were conspicuous by their absence in a statement about the future of our country and its place in the world order.

Why not mention these things? There is a pattern. They all require unprecedented international collaboration. These are not problems which can be fixed by strengthening borders and building walls. And so it was easier not to mention issues like these at all.

Happily, May's vision for Brexit is neither fixed nor inevitable. We've triggered Article 50, but it's up to all of us what comes next. And as co-leader of the Green Party, I'll be fighting for progressive outcomes every step of the way.

We'll fight in parliament to make sure we get a new Environment Act, not only preserving our environmental protections but strengthening them. We'll scrutinise trade deals to make sure they have rights for workers and the environment enshrined at their core. And we'll push back against any attempts to turn the UK into a tax haven for the ultra-rich, widening inequality in an already divided country.

But as important as tax, trade and legislation are, let's never forget that what's really being negotiated are people's lives. The impact this is having on millions of people, often the most vulnerable, is unacceptable, and I'll be standing with my neighbours in the messy years ahead. This could be our most important work. Standing with each other and challenging hate. This is even bigger than Brexit.

Today offers no break from the grim trend of the last year or so. We're seeing coded immigrant bashing turn into explicit xenophobia and hate crime, in a world where the far-right is on the rise. EU nationals are used as bargaining chips.

A whole generation of young people – who overwhelmingly voted to Remain – are forced to watch their future implode. For such people, the rhetoric of May's Article 50 statement must have seemed especially hollow.

Jonathan Bartley is co-leader of the Green Party