West Australian Liberal Party leader Colin Barnett has become the state’s 29th premier.

Barnett, a member of parliament for 18 years, was sworn in as the head of the Liberal-Nationals minority government by West Australian Governor Ken Michael at Government House in Perth.

The premier’s 17-member cabinet, comprising 13 Liberals, three Nationals and independent Churchlands MP Liz Constable, will lead a government with a narrow margin over Labor, which will hold more seats in the Legislative Assembly than the Liberals.

With the Electoral Commission yet to declare several seats, the current tally is Labor: 28 seats; Liberals 24; The Nationals four seats and Independents three.

The Nationals agreed to support the Liberals after the September 6 election left neither major party with enough seats to govern in their own right.

Mr Barnett has said parliament will sit before Christmas and introduce priority legislation to repeal Labor’s truth in sentencing laws, where sentences are immediately cut by one third.

There would also be bills, to “save” Royal Perth Hospital and to repeal Labor’s regulation of brothels and its drug laws.

Former treasurer Eric Ripper is Labor’s new parliamentary leader.