Prominent Australian lawyers and corruption experts have joined the push for Tasmanian political parties to disclose donations from the gambling industry before Saturday's election.

The group includes a former Supreme Court judge, a former director of public prosecutions and an ex-premier of Western Australia, who are concerned about the undue influence of pro-pokies groups.

They have signed an open letter to Tasmanian Liberal leader Will Hodgman and Labor leader Rebecca White, urging them to disclose donations from the gambling industry before March 3.

Geoffrey Watson SC, a barrister who has previously worked with the New South Wales Independent Commission Against Corruption, said it was clear interstate pro-pokies groups were pouring money into the Liberals' campaign, but there was no legal requirement for disclosure before the election.

"It's very plain that interested parties are deliberately attempting to control the outcome of the election by funding one side of the Parliament House very heavily," Mr Watson said.

"It's just wrong, because they've got the money to have their say and there's got to be some sort of broader control to prevent this from occurring."

He said Tasmania was lagging behind other states and needed broader controls around donation disclosure.

RMIT ABC Fact Check recently found it was a "fair call" that Tasmania has the weakest political donation laws in the country.

There are no state-based restrictions on political donations in Tasmania, and because Australian Electoral Commission disclosure of political donations for a given financial year does not occur until the following February, sometimes a donation may not be made public for up to 19 months.

Mr Hodgman has said he would disclose donations received by the Liberals in accordance with the law, meaning voters would not know until well after election day how much money the party was receiving from the gaming industry.

The open letter was released by the Australia Institute, a think-tank formed in 1993 by a left-leaning academic.