At elections, political tribes join together to promote their own policies and criticise those of their opponents. That’s the nature of elections. But there are always individuals who enhance parliament. And there are always policies upon which every party can agree.

One is democracy, and the right of every adult to vote. At every election the future of our country is at stake. But on this occasion even more than usual.

When the nation voted on Brexit it did so on a diet of fiction and undeliverable promises. As the facts become known, it’s extraordinary that a new vote is denied: extraordinary, and frankly undemocratic.

People have strong views on Brexit. Mine are very clear. I believe that leaving the European Union is the worst foreign policy decision in my lifetime. It will affect nearly every aspect of our lives for many decades to come and it will make our country poorer and weaker, and the individuals within it. It will hurt most those who have least.

Never have the stakes been higher, especially for the young. Brexit may even break up our historic United Kingdom. Within a few years, Scotland may leave the union. Northern Ireland may unite with the south. Both may do so in order to remain within the EU.

Our young generation has already recognised this – by registering to vote in record numbers. And your vote is absolutely crucial – for you have the longest lease on our country’s future, and our place in the wider world. So my message to you is very clear: don’t allow your future to be shaped by others, with no input from yourselves. You – every single one of you – can make a difference to the election result.

So don’t hang back. Don’t wait until Friday 13 December and then regret that you didn’t make a choice.

To vote means to choose. So choose the future that you believe in. Vote for the candidate who you believe will best represent your own views and your own aspirations in the next parliament.

I was in politics for many years, and – believe me – no single party has a monopoly on wisdom. I am a Conservative, but there have always been policies of other parties with which I agreed. That is politics as it truly is.

Tribal loyalty has its place. It can be good and honourable. But sometimes you need to vote with your head as well as your heart. To vote for your country and your future. This is such a time.

Michael Heseltine is a giant of the Conservative party, a giant of successive Conservative governments – including my own when he was deputy prime minister. He has always been fearless in protecting the best long-term interests of the UK. Michael is, truly, one of a kind – and a very wise one of a kind.

David Gauke, Dominic Grieve and Anne Milton – all of them principled, decent, talented human beings – were forced out of the Conservative party, and are now fighting this election as independent candidates. But let me make one thing crystal clear: none of them left the Conservative party, the Conservative party left them.

Without such talent on its benches, parliament will be the poorer, which is why – were I resident in any of their constituencies – they would have my vote in this election.

• John Major is a former prime minister. This is an edited extract of a speech he gave to the Vote For a Final Say rally on 6 December 2019