Australia's most senior legal officer, George Brandis, is acting as a scrutineer in the last undecided seat in the federal election, where the Coalition is increasingly confident of a win.

Incumbent Ewen Jones took the lead in the Townsville-based seat of Herbert for the first time on Wednesday afternoon before the lead changed several time before the vote count was concluded for the day.

Prime Minister Malcolm Turnbull said he was confident the Coalition would secure the Queensland seat giving it a slim majority — two seats clear of a hung parliament.

"It's too early to be entirely definitive about the final outcome but we are confident, optimistic, that Ewen's lead will grow as the final thousands of votes are counted," Mr Turnbull said.

"Which would mean that we would have a majority of 77 in the House of Representatives."

The ABC election computer is yet to call Herbert.

Senator Brandis, the Attorney-General, was spotted scrutineering during the vote count on Wednesday.

Scrutineers are appointed by candidates to oversee the sorting and counting of votes and check any irregularities.

Labor's candidate for Herbert, Cathy O'Toole, had previously been ahead in the count, but postal votes in the seat with a significant military contingent had been falling in the Government's favour.

Earlier, Labor's Steve Georganas claimed victory in the South Australian seat of Hindmarsh.

Opposition Leader Bill Shorten heralded him the "hero of Hindmarsh", but the sitting Liberal MP Matt Williams was not willing to concede defeat.

Mr Williams said there were still thousands of votes to be counted.