Alexandria Ocasio-Cortez vows to vote against Democratic leader Nancy Pelosi on first day in congress

Left-wing congresswoman to begin career in Washington by defying her party leadership

Alexandria Ocasio-Cortez today became the youngest woman elected to Congress (AFP/Getty)

Alexandria Ocasio-Cortez has said she will vote against the House rules package being proposed by Democratic leader Nancy Pelosi.

The 29-year-old left-wing congresswoman, viewed as a rising star in the Democratic Party, will begin her career in Washington by defying her party leadership as they launch their ambitious policy plans.

Ms Ocasio-Cortez has said she will not support new guidelines tabled by her party that include a provision known as "PAYGO” or “pay as you go” which requires new spending to be offset by cuts elsewhere or increases in revenue.

Critics say the proposals will self-impose an obstacle to increased government expenditure with minimal upside, while those who support it believe it would prevent reckless spending.

“Tomorrow I will also vote No on the rules package, which is trying to slip in PAYGO,” Ms Ocasio-Cortez tweeted.

“PAYGO isn’t only bad economics as [US Representative] Ro Khanna explains; it’s also a dark political manoeuvre designed to hamstring progress on healthcare and other legalisation.

“We shouldn’t hinder ourselves from the start.”

Eighteen Democrats would need to vote against the package for it not to get passed

Ms Ocasio-Cortez, a New York Democrat, shocked the party when she won the June primary against Joe Crowley, a 20-year Congressman.

She supported Ms Pelosi for speaker because she was 'the most progressive candidate' for the position.

Ms Ocasio-Cortez has however been at odds with party leadership and has vowed to maintain her ideological beliefs when in Washington.

In November Ms Ocasio-Cortez joined a group of activists who staged in a sit-in protest at Democratic leader Nancy Pelosi’s congressional office.

Sunrise, a progressive environmentalist movement, organised the protest to push Democrats to act more decisively on climate change now that they have control of the House of Representatives.