Attorney-General George Brandis believes the High Court will not deal with the citizenship crisis that has embroiled seven MPs and senators until October, leaving Malcolm Turnbull's one-seat majority hanging in the balance.

The Parliament has already referred Nationals senator Matt Canavan, Greens senators Larissa Waters and Scott Ludlam and One Nation Senator Malcolm Roberts, as well as Deputy Prime Minister and Nationals Leader Barnaby Joyce to the court.

The High Court will have a directions hearing on the matter on Thursday, where a judge will get the parties together and agree to a timetable over the various steps towards the hearings.

On Sunday Mr Brandis told Sky News: "The Commonwealth will be asking the court to deal with the matter urgently."