The union movement is fiercely leaning on Labor's Left-faction MPs to oppose a suite of free-trade deals to come before federal Parliament unless they can secure protections for Australian workers.

A grouping of Socialist Left unions - which include the Australian Manufacturing Workers Union, United Voice, the Community and Public Sector Union and the Australian Services Union - has written to MPs ahead of Labor's caucus meeting on Tuesday.

The union movement will continue its campaign against free trade agreements that they believe sell-out workers. Credit:Vince Caligiuri

While the unions say they are supportive of the "trade of goods", they remain steadfastly against "the trade of people" through provisions which would allow foreign workers greater access to projects in Australia.

Labor has flagged it will support the passage of three new free-trade agreements - with Indonesia, Hong Kong and Peru - but has reassured unions it will seek concessions on labour market access before waiving them through Parliament.