A battle is brewing within WA Labor over the position of party President, with Premier Mark McGowan's preferred candidate, United Voice Secretary Carolyn Smith, facing a challenge.

Ms Smith is being opposed by Maritime Union official and former federal Labor candidate Adrian Evans, who ran for the seat of Hasluck in 2013.

Mr Evans also ran for party President in 2014 but was beaten by Willagee MP Peter Tinley, who is now the Minister for Housing, Veterans Issues and Youth.

Factional power test

The ballot for President is the first real test of which factional grouping has control of the ALP, after a number of unions realigned earlier this year.

Progressive Labor is backing Adrian Evans. ( Supplied: Facebook )

A new grouping, known as Progressive Labor - which is backing Mr Evans - has the common goal of curbing the power of the party's left faction, led by Ms Smith.

Progressive Labor comprises a number of unions, which were previously in opposing factions, and includes the Maritime Union of Australia, the CFMEU, the Transport Workers Union, the Shop, Distributive and Allied Employees Association and the Australian Workers Union.

They have joined forces in an attempt to limit the influence of Ms Smith over party preselections and key appointments to the ALP's decision-making bodies.

A fortnight ago the Premier raised eyebrows when he publicly backed Ms Smith to replace Mr Tinley as President for the next two years.

Mr McGowan, who does not normally get involved in internal party matters, was glowing in his praise of Ms Smith.

"She's a terrific person, and a great contributor and very bright and very collaborative, and I'd like to see her elected," said Mr McGowan.

Social media campaign

Under party rules, candidates are not allowed to campaign in the media or give interviews, but that has not stopped them from being active on social media.

Rival Facebook pages have been created, in a bid show off key backers and attract support.

The winner will be determined by a vote of all Labor Party members, with the count taking place on June 20th.

A third candidate Vicky Burrows has also nominated for the position.

Ms Burrows was fifth on the party's South Metropolitan Upper House ticket in the March election.