I voted for Corbyn to become Labour leader but I can't in the general election unless he changes a few things

It's time to be honest about Brexit, immigration, education and crime. For instance: the reason local people don't 'want to work' may have something to do with the fact that if you live in a three-bed semi in Boston, Lincolnshire, paying council tax, rent, bills and PAYE, you simply cannot afford to work on the minimum wage, whereas if you're a young kid from Portugal who doesn't mind sharing a ramshackle caravan with six other migrants, you can

Jeremy Corbyn's Labour Party has seen its support increase by four points (PA)

OK, hands up: I voted for Jeremy Corbyn to be the new Labour leader in 2015. My reasons were sound at the time: I woke up in the night in a cold sweat, realised my politics were beginning to drift to the right, decided that was a betrayal of all my family have stood for over the past 100 years and concluded that yes, I wanted Jezza to be our Great Leader. Then I went back to sleep.

I should emphasise that as a long-term resident of Islington North (still bizarrely and endlessly portrayed in the media as middle class and out of touch – have these people ever been to Holloway?), Jeremy is a decent constituency MP. I've contacted him twice and he dealt with both queries. Once, at a book launch, he made a joke about my then-toddler son drowning him out by making a din. I have little doubt he's a good, well-meaning, honest man. That's why when I drove through Tufnell Park the other day and Jeremy cycled past in the other direction, I didn't suddenly veer to the right.

But – how can I put this? – Jeremy's made a few mistakes. I don't have time to list them all, so let me mention one, because it's the biggest mistake and symptomatic of his biggest flaw. His appointment of Seumas Milne has been an unmitigated disaster. Milne – who is, like many on the left, upper middle class and guilt-ridden about it to such a degree that he skates close to becoming a proto-Stalinist – simply has no understanding of modern Britain. If Corbyn is to triumph, Milne must go (hopefully not back to the Guardian.)

If Corbyn can rethink a few key policies (and come up with a few new ones), then there's still a slim chance he could cause the biggest political upset since – well, since Trump became President. So as a favour, Jeremy, and because I don't want to see you end up like Ed Miliband, who hangs around my son's school gate smelling of failure, let me help.

First, Brexit. Simply bleating about hard Brexit and soft Brexit is a waste of time; no one knows what any of it means. We're leaving the EU, so de-politicise the process and get what's best for Britain: keep the better laws, dump the stupid ones, allow EU migrants to stay without demanding a similar guarantee for UK residents abroad because it's the right thing to do.

At the same time, Corbyn and his team must accept that being concerned about migration and militant Islam doesn't necessarily make you a racist. British citizens come in all colours, and indeed the BME communities are often hit hardest when it comes to schools, the health service, transport and housing.

Furthermore, although almost everyone accepts that migration has huge benefits, we should be honest about the problems it can bring. There's a funding crisis in schools not because (or not only because) the wicked evil Tories cut funding, but because there are so many more pupils. Young migrants who work do contribute to the economy, but if they stay they will also eventually become sick, and pensioners; also, of course, luring the brightest and best migrants from across the world – not just the EU – has an impact on the country they left behind for the delights of a damp bedsit in Edgware. The only migrants I want banned are the rich ones who are buying up half of London.

As for agricultural workers, the reason local people don't "want to work" may have something to do with the fact that if you live in a three-bed semi in Boston, Lincolnshire, paying council tax, rent, bills and PAYE, you simply cannot afford to work on the minimum wage, whereas if you're a young kid from Portugal who doesn't mind sharing a ramshackle caravan with six other migrants, you can.

We should continue to allow migration, therefore, but also raise the minimum wage for all agricultural workers and push foreign languages in our schools much more aggressively. There's no point fighting for the right for our kids to be baristas from Munich to Madrid unless they can speak the lingo.

This brings us to education. Whose bright idea was it to encourage 50 per cent of children to attend university? (Hint: Blair’s). The university system needs a revamp – shorter, sharper, more practical courses, an end to student loans, and a greater emphasis on free thought. Any applicant who is unable to explain why free speech for Islamists, alt-right wingers and Julie Bindel is a good thing should be classed as a snowflake and given a job just outside Boston, Lincolnshire.

It's clear Scotland wants to go its own way, and the demographics of Northern Ireland suggest the six counties should be allowed to join the 26 south of the border. A referendum on the future of the whole UK – on which the English are allowed a vote – is the only way forward. If Scotland does leave, we make a deal with Spain: approve Scotland's application to the EU and you can have Gibraltar (as long as you give up Ceuta and Melilla). Sorry, tax-dodgers.

Labour is often portrayed as being soft on crime. Strange, then, that the last Labour government introduced so many new laws, not all of them well thought-out. So here's a suggestion: ban the term "hate crime". If some yob pulls off a woman's burqa in the street, come down on them like a ton of bricks – but have the same harsh penalties for insulated communities of second generation immigrants who attack "outsiders" in certain areas. It's all hate.

If Jeremy will agree to my radical manifesto, not only will I vote for him on 8 June, but I'll stake my modest fee for this article on him to win and be our next PM. If, on the other hand, he can make no such guarantee, nor can I guarantee my vote. The trouble is, being genetically unable to vote Tory, despising Ukip and the Lib Dems and too much of a hard realist to vote Green, who on earth would I vote for? Unless I stand as an MP against Jezza myself?

Hmm, I ponder...

Mark Piggott is an author and journalist