A Resolve Political Monitor survey, published in Nine newspapers on Tuesday, showed 47 per cent of voters backed a plan to enshrine an Indigenous voice in the constitution.

The figure, based on more than 3000 responses during a month from late December, was down from the 53 per cent who supported the move in August and September.

Some 30 per cent said they didn’t back the constitutional change, up from 29 per cent in the previous survey.

A growing number of people were undecided, with the cohort swelling from 19 per cent to 23 per cent.

The survey comes as the opposition ramps up its attacks on the government over a claimed lack of detail on the proposed body.

Indigenous leader and leading “yes” campaigner Noel Pearson on Monday dismissed the call for more detail as a diversion, adding that a referendum failure would permanently harm reconciliation efforts.

Prime Minister Anthony Albanese, who released the wording of the proposed referendum question at the Garma festival in July, has said parliament would decide how the advisory body operated if the referendum was successful.

The National Party has declared it will not support the referendum, while the Liberal Party is yet to set out a formal position.