If you were a 16 or 17-year-old is Scotland, you probably felt quite annoyed at being left out of December’s General Election.

If it had been a Scottish Parliament or local council election you would have been allowed to vote, but for Westminster elections you have no such right.

This extension of the Scottish franchise came about post the Independence referendum when, for the first time in the UK, this group of young people were included and given a voice in our democratic processes.

The way in which they spoke up and got involved in the debate and the vote changed the views of leading politicians such as Ruth Davidson and arguably the Scottish public to be wholeheartedly on board: backing these young people in the sovereign right of the Scottish people to decide by who they are governed, at least at Holyrood and council level.

Now, 16 and 17-year-olds in Wales have officially secured the right to vote for Senedd elections, after a crucial piece of legislation received Royal Assent last Wednesday.

The Senedd and Elections (Wales) Act has officially entered on to the statute book – the biggest change to the franchise in Wales since the reduction of the voting age from 21 to 18 in 1969.

It follows years of campaigning from Electoral Reform Society (ERS) Cymru and a coalition of youth and civil society campaigners, including the NUS and the British Youth Council.

But a big part of how the argument was won was the success of votes at 16/17 in Scotland.

Our colleagues at ERS Cymru successfully lobbied parties to back votes at 16/17 during the last Senedd elections, and later provided evidence to the Welsh consultation on extending the franchise, drawing heavily on the Scottish experience: of packed stadiums full of young people in the 2014 Indyref and high turnout since.

UK-wide, the Society works with the British Youth Council and other youth focused organisations – including on the All Party Parliamentary Group on Votes at 16 – to make the case for change.

There, SNP, Greens, Labour and some Conservatives are making the case for a UK-wide shift on this policy.

There’s more good news (hopefully) soon to come, in Wales at least. A separate piece of legislation is currently progressing through the Senedd on extending the right to vote for 16 and 17-year-olds for the next Welsh local government elections, due to take place in 2022.

The movement for a fairer franchise is growing. Sixteen and 17-year olds can already vote in Guernsey, Jersey and the Isle of Man, as well as here in Scotland.

Why does it matter? Firstly, it won’t surprise you that democracy is struggling.

A survey by the Hansard Society last year found that nearly three quarters of people felt our system of government needed improvement.

It’s clear our institutions need an overhaul – and increasing engagement is vital to making sure they work for all of us.

In Scotland, 16 and 17-year-olds rightly have a voting influence over critical issues that affect their future, such as health, education and the economy. As we’ve already seen, this is a boost for our democracy as a whole – strengthening citizenship and boosting political engagement.

Citizenship education is also stronger in Scotland than much of the rest of the UK. And there are lessons that can be learnt in Westminster. The numbers speak for themselves.

A survey commissioned by the Electoral Commission following the Scottish Independence Referendum (in which 16 and 17-year-olds were entitled to vote) found that 75 per cent had taken part.

These young people planned to stay politically engaged. A survey carried out in 2015 found that 67% of 16 and 17-year-olds in Scotland said they’d vote in a general election if given the chance.

Twenty years after devolution both Scotland and Wales have significant powers to do things differently and change the way elections work – all of which makes England look increasingly isolated on this.

It’s a gross constitutional injustice that 16 and 17-year-olds will continue to be denied the vote for Westminster elections.

It’s time for the government to get behind this win-win policy – and we hope Scottish MPs will lobby hard for this change. Unfortunately, a generation of young people in England and Northern Ireland are being left behind, while Scotland and Wales make major strides in strengthening democracy.

The past year has shown how much young people care – about issues like climate change, education, rights and more. But this isn’t about the politics: it’s about building a truly united franchise for the UK.

If the UK Government wants to preserve the union, they would do well to stop alienating Scotland’s young people.

Instead of chucking up barriers to people voting through imposing mandatory voter ID – a policy rejected across Holyrood – Westminster should look at the efforts being made in Wales and Scotland to build a better, fairer democracy.

Willie Sullivan is Senior Director, Electoral Reform Society Scotland