It is now almost 40 years since the people of Britain last had the opportunity to vote on our membership of the European Union.

Then, of course, it was the European Community, and it has changed almost beyond recognition in the decades that have since elapsed. What was once a six-nation trading bloc has become a European Union of 28 countries.

But despite these changes, and despite the many promises that have been made for a fresh vote, none has taken place.

At the last election, the Liberal Democrats promised a referendum on our membership and at times Labour have done so, too. Even Peter Mandelson demanded an in-out referendum only last year.

Now we have the opportunity to write into law David Cameron’s commitment to such a referendum after the next election.

The Bill to achieve this has passed the House of Commons despite the attempts of many Opposition members to block it. In the end it was approved by a huge majority.

Now, incredibly, there are those in the unelected chamber of our Parliament who are seeking to thwart the clearly expressed view of the elected chamber.

It beggars belief that those who have not been elected should try to deny the people of our country the right to vote on this vital issue. Yet that is precisely what is about to happen.

In the House of Lords, Labour and Liberal Democrat peers plan to obstruct and defeat the Bill by weighing it down with fanciful amendments. They have tabled more than 50 of these, which would slow, and potentially stop, its passage. They range from the requirement for a petition signed by a million people to having the question translated into Cornish. Even Lord Foulkes, who has tabled a majority of the amendments, said yesterday that he didn’t support most of them.

My colleague, Lord Trefgarne, remembers the last time a Bill providing for a referendum on our membership came to the Lords. It was in 1975 and it passed through committee in a single day, without a vote.

There is no need for the committee stage of the current Bill to take any longer. It is already as straightforward as it can be — a legally requirement for a referendum before 2017, with a simple question: in or out.

And, of course, if by any unhappy chance the obstructive efforts of the Opposition were to succeed, it would be nothing short of an affront to the democratic process for which the Parties concerned, and their leaders, would be held to account.

In four years David Cameron has already achieved more in Europe than Labour managed in the previous 13. He has vetoed a treaty that would have harmed our interests. He has secured the first ever EU budget cut, even when his opponents said he couldn’t. And we no longer contribute to the bailout funds that saw the UK taxpayer foot the bill for the crises in Europe. Labour signed us up but it is Mr Cameron who is delivering real change.

These are all huge achievements but they are not enough.

The people of our country deserve a say on this vital question. This Bill would provide it. The House of Lords should not obstruct it.