SYDNEY (Reuters) - Support for Australia’s once-influential far-right One Nation party plummeted in the past week after a series of scandals and internal ructions, a widely watched poll showed on Monday, weeks out from a general election.

A Newspoll for The Australian newspaper showed One Nation on course to win just 4 percent of the primary vote at the May 18 election, down 2 percentage points from the previous week.

The poll also showed that the conservative Liberal-National coalition government remained on course for a heavy defeat by the center-left opposition Labor party.

Support for One Nation peaked at 11 percent of the primary vote two years ago, when it held the balance of power in the upper house Senate.

However, One Nation’s influence waned amid internal divisions and its fortunes suffered even further after two prominent members allegedly sought millions of dollars from the U.S. gun lobby in exchange for weakening Australia’s strict gun control laws.

That opens the way for an intense battle for the right-wing vote as small parties and independents compete with the Liberal and National parties for a handful of potential seats.

Conservative voters would typically support the government but the Newspoll showed Prime Minister Scott Morrison had so far failed to win them over.

The Newspoll showed Labor retained a lead of 52 percent to 48 percent over the government on a two-party preferred basis, where preference votes are distributed until a winner is declared.

The findings were unchanged from the previous poll last week, despite Morrison’s efforts to attack Labor’s taxation plans.

Morrison has led his pitch to voters with his government’s economic credentials, framing the election as a referendum on its record of managing Australia’s finances.

Morrison’s pre-election budget earlier this month promised tax cuts for low- and middle-income earners, while projecting the first budget surplus in more than a decade.

Seeking to limit the government’s appeal, Labor promised to match the tax cuts for middle-income earners and pledged bigger concessions for lower-paid workers.

It will fund the income tax cuts by curbing capital gains tax discounts, seeking greater taxes from multinationals and banks, and scrapping a favorable tax scheme for property investors called negative gearing.

Newspoll surveyed 1,697 voters nationally from April 11-14.