The Government needs to answer a question: What evidence have they that the young people in this specific age group in England and Wales are less mature, less responsible and less well informed than their compatriots in Scotland? Secondly, if this is a truly United Kingdom, how can they justify discrimination in such an absolutely crucial matter as voting, which will exclude young people south of the border?
I asked this question in the House of Lords and it was evident that not a single peer had an answer.
The young people of England and Wales are just as mature, responsible, well informed and ready to take on some of the responsibilities of adult citizenship as the young people of Scotland. It has been proved in Scotland and all parties in Scotland have now accepted that it has been proved.
The Lords looked at this evidence, they debated the issue at length, and voted 221 to 154, a substantial majority of 67, to extend the franchise for all council elections in to give 16-year-olds a voice throughout England and Wales.
The experiences of Scotland have changed the landscape over the last 18 months. Hitherto, those of us Liberal Democrats who have campaigned for years for this incremental reform have done so on a theoretical but principled basis. Now we have also firm practical evidence. As a result we have recruited new allies in the other political parties.
Not only did this age group defy all predictions by registering for the referendum in their thousands but 75% of them turned out to vote, eclipsing those in the 18-24 age bracket. Indeed, within their school and home environment - before so many typically leave that familiar environment for employment or education reasons - they were much more likely to debate the issues seriously, and build upon their previous citizenship courses.
There is also solid evidence that if they start voting at this age they are more likely to continue to register and vote later on.
The outcome was so persuasive that even the Conservative leader in the Holyrood Parliament became an enthusiastic convert, promising to continue to encourage the Prime Minister to change his mind.
Clearly, it is now only a matter of time before the franchise is extended in this way. The lesson of the long, tortuous and piecemeal extension of votes for women demonstrates the inevitability of eventual success.
Meanwhile, English and Welsh MPs, who have resisted so far, have an awkward truth to face. If they cannot answer my question they will have to look their 16 year old constituents in the eyes and tell them that they don't think that they are as capable as their Scottish compatriots.
Today, as we vote in the Lords to expand the electorate, the Government has many questions it should prepare to answer. So far they have avoided the debate, hiding behind their majority in the Commons to silence progress. The evidence has shown they are on the wrong side of history and today we wall call on them again to give young people the voice they deserve.
Lord Tyler is a Lib Dem peer, and the party spokesperson on political and constitutional reform