Pauline Hanson has lashed the Greens for using Punjabi on campaign signs ahead of the federal by-election, insisting that English should remain the primary language. 

The One Nation leader claimed the Greens' decision to display a sign in Punjabi undermines the unifying role of English as Australia's national language.

'What's interesting in this by‑election are the corflute signs that are popping up across the electorate,' she wrote on Facebook on Thursday. 

Early voting for the NSW seat of Farrer opens next Tuesday, with voters scheduled to head to the polls on May 9. 

The vote follows the resignation of long-serving former Opposition Leader Sussan Ley, who held the seat for 25 years after she was first elected in 2001.

'The Greens have erected the following signs, appealing to the Indian community in Punjabi,' Hanson said. 'The Greens ignore the vital need to use English for those who want to call Australia home.'

She argued that English proficiency is especially important during election campaigns, where voters must weigh up candidates and their policies. 

'English is critical for economic, social and practical survival, especially during elections where debate and policies help voters form a view on who is best suited to lead a community or region,' she wrote.

Hanson also took aim at the Greens' wider agenda.

'Remember the Greens stand for open borders, mass migration and further division in this country,' she said.

The Greens' signs promote their candidate Richard Hendrie, encouraging voters to 'Vote 1' and spelling out party priorities. 

One of the Punjabi signs says the Greens support social justice, oppose discrimination and stand for better education, healthcare, environmental protection and cost‑of‑living relief.

Another sign highlights the party's stance on social wellbeing, refugee protection, environmental action and ending political corruption.

However, the 2021 Census shows Punjabi speakers make up just 1.2 per cent of Farrer's population. 

The rural electorate stretches across south‑western NSW, taking in regional centres such as Albury, Griffith, Leeton and Deniliquin, and has been a conservative stronghold since its creation in 1949.

The by‑election is shaping up as a fierce contest, with One Nation's David Farley and independent Michelle Milthorpe among the frontrunners.

One Nation remains ahead of the Coalition in recent polling, with a new YouGov survey putting the party level with Labor nationally on a 27 per cent primary vote.

Liberal sources say their candidate, Albury councillor Raissa Butkowski, is an outside chance, as the party seeks to win back ground by highlighting One Nation's controversies - including the fallout over the employment of convicted rapist Sean Black, who was sacked following public backlash.