A former Liberal leader, a prominent comedian and an award-winning novelist are among those who have signed an open letter calling on the federal government to abandon plans to cut unemployment payments.

Thirty-four notable Australians – also including economists, academics and religious leaders – have put their names to the letter urging Prime Minister Malcolm Turnbull to change course on the Newstart benefit. They're also calling on Opposition Leader Bill Shorten and Labor to stand firm against the government's plans.

Prime MInister Malcolm Turnbull can expect pressure for a parliamentary vote from Liberal MPs who support marriage equality if the plebiscite is blocked. Credit:Getty Images

Former Liberal leader John Hewson, comedian Corinne Grant, Miles Franklin Prize-winner Anna Funder, businessman John Menadue and former politicians Carmen Lawrence and Cheryl Kernot have signed the letter.

Other signatories include economist David Morawetz, Uniting Church president Stuart McMillan and respected academics Barbara Pocock, Spencer Zifcak, Frank Stilwell, Marian Baird and John Buchanan.