As you read this I am with statesmen and dignitaries from more than 100 countries at the Rio+20 UN Conference on Sustainable Development. There are leaders from countries with a wide range of different democratic systems and almost overwhelmingly they are united by one belief: that the people who make the laws should be elected.

It seems bizarre to think that, in Britain in the 21st century, that should still be a controversial statement, and yet the majority of politicians in our own Parliament are not elected. They sit in the House of Lords, a body of appointed politicians that is growing at a startling rate and has no democratic mandate.

The Independent's revelations this week have shone an important light on the sometimes murky world of our second chamber and raised very serious questions. It should be stressed that the vast majority of peers obey the rules and that MPs, still tainted by the expenses scandal, need to be careful judging the behaviour of those in the Lords. But it does provide us with another opportunity to question why we think this is the best way to govern our country.

Lloyd George once described the House of Lords as being "a body of 500 men chosen at random from amongst the unemployed". In the years since he made that remark all that has really changed is the number – we are now pushing nearly 1,000 peers who get £300 tax-free a day just for turning up, more than half from the ranks of retired or failed politicians. For those retired MPs in the Lords, this amounts to a £1m top-up to their pensions.

Of course among our peers there are those with valuable experience and expertise who have made a vital contribution. But we can protect that expertise and still end the existence of an institution whose current composition is an affront to the principles of openness which underpin a modern democracy.

Fortunately, we are now in a position to create a democratic second chamber. The Government is shortly to publish its proposals for Lords reform and all three major political parties put a democratic House of Lords in their manifestos at the last election. We just need politicians to do what they are always promising to do and put party differences to one side.

When Ed Miliband gave his first speech as party leader to the Labour conference he promised a "new politics" and to "change the way government works". The Coalition Government is giving him the opportunity to do just that, to put old-fashioned tribalism aside and help deliver something that his party has long campaigned for.

And any Conservatives who are uneasy about the reforms should see this as delivering on the promise they made in their 2010 manifesto to deliver "a total overhaul of our system of government, so that power is passed from the politicians at Westminster back to the people of Britain".

It has been said by some that there are more important things for the government to be focusing on. I agree. Our No 1 priority will always be protecting people in this country from the global economic crisis. But getting three political parties to deliver on their promise of more democracy shouldn't be time-consuming if everybody keeps their word.

We have a second chamber in desperate need of change, we have the political agreement, and we have the opportunity. To all those who say now is not the time for reform the question has to be, "If not now, when?"