Mr Green agreed the Electoral Act allowed voters to put a No1 only next to their preferred candidate, but the ballot paper told voters to number candidates at least from one to five or one to seven, depending on the electorate.

''In all the official publicity the Electoral Commission put out, we said to voters that you should number at least as many candidates as there are vacancies,'' he said.

''In our election guide, there was in the detail a statement to the effect that a single first preference is a valid vote but what we recommend is that you should number at least the number of vacancies.''

Mr Green said it was a perennial issue. ''We get this every election. People say, 'Why don't you tell people you can just put a tick or first preference?''' he said.

''An Assembly committee looked at that and they said, 'Yes, there is this apparent contradiction in that.' But the Assembly wants us to keep doing what we did this time and what we've done at every election effectively, which is to have this message you should number from one to five or one to seven.''

Mr Green said the Hare-Clark system worked best the more preferences voters expressed.

''Voters aren't confused. Voters, I think, really understand the preferential system in the ACT and they use it to good advantage,'' he said.

Mr Green said the informal vote so far at this election was 3.2 per cent, compared with 2.65 per cent in the 2004 poll. ''It's still very low.''

So far, the informal vote is highest in Brindabella, at 4.1 per cent.

Mr Green also said he did not believe putting Independent candidates in an Ungrouped column on the ballot had disadvantaged them.

''Candidates who aren't members of major parties, who don't have a high profile, regardless if they are in an ungrouped column or a non-party grouped column or a new party that's not very well known: they're just simply not going to get very many votes and I really don't think there's any systematic bias in the way that Independent candidates are treated.''