David Owen chose the weekend of the Lib Dem conference to offer his personal advice about the AV referendum. Having attacked the first-past-the-post voting system so vociferously for many years, it will seem odd to some people that he now urges support for this system on 5 May. He says that he hopes for a referendum with an option of a proportional representation system instead.

Almost all those people who have consistently supported the cause of electoral reform for much longer than he has take a different view. It is very clear that voting against change on 5 May will mean sticking with the present voting system for the foreseeable future. It is incredibly hard to overcome the self-interested nature of most sitting MPs in order to get a change in the voting system. The referendum will be the first chance that voters will have had to change the system since it was effectively introduced in 1872 in wholly different political circumstances to those of today.

A change to the alternative vote system was recommended by a Royal Commission as far back as 1910. It was recognised 101 years ago that first-past-the-post doesn't work when you have more than two political parties. A "no" vote in the referendum will leave us with the voting system that was appropriate for the 19th century not the 21st.

Owen was simply being disingenuous when he followed the line of opponents of electoral reform and suggested that votes for a party that comes second or third will have "more weight" than votes for a party that comes first. The whole point of the reform is that every vote will be of equal value and people will not have to fear "wasting" their votes on candidates who may not win. He even repeated lines saying that more power may go to extremists with AV when the reverse is true. He fails to explain why the BNP urges its supporters to vote "no".

Owen further argued that AV was rejected by inquiries. AV was in fact a part (but only a part) of the recommended system proposed by the Jenkins Commission in 1998. It is of course widely used by political parties including all those supported by Owen over the last 30 years when they are choosing a single person.

There are a number of completely bogus arguments against AV now being made by those who are determined to hang on to first-past-the-post. At the same time, there appear to be no coherent arguments emanating from the same sources to defend this system. We hear claims from others in the "no" camp that AV is "un-British". One problem with this claim is that the system is used to vote for leaders and candidates in the Conservative party (as well as almost all other British political parties) and other organisations representing 14 million people in Britain. I am waiting to hear David Cameron declare his own party to be "un-British" because it used AV to choose him as leader.

The most absurd claims from the "no" campaign are that "it would cost too much to count the votes if we used AV". This claim is probably worthy of many dictators. They could say that their country could only afford to count the votes for the governing party and there wasn't enough money to count the votes for opposing parties. The argument is a disgrace.

Owen does not have an alternative strategy to deliver PR. He led his closest followers in to a political cul-de-sac when as SDP leader he failed to respect the referendum of SDP members on their future. I doubt he will have many followers on this issue.

But those seeking a fairer voting system may be rather more dismayed if the Guardian is correct that there are difficulties getting Ed Miliband and Nick Clegg working together in support of the referendum. Political rivalry over other issues should not prevent all supporters of reform from campaigning for a cause on which they agree. Lessons should be learned from the Scottish referendum in 1997 when Labour had to campaign with its great rivals in the SNP (as well as the Liberal Democrats) to secure a Scottish parliament.

The leaders of the Labour party, the Liberal Democrats, the SNP, Plaid Cymru, Ukip and the Greens are all on the "yes" side in this referendum. Against them are the leaders of the Conservative party and the BNP. With only two choices in the referendum, the leaders who want change need to show that they can work with each other on this crucial issue even if they differ quite fundamentally on other issues.

• David Rowntree: AV won't improve our electoral system