Former federal politicians have threatened to launch court action to prevent the federal government from reining in their taxpayer-funded travel entitlements and from blocking ''windfall'' pension increases to retired MPs and senators.

The Association of Former Members of the Parliament of Australia has attacked plans to impose new limits on the number of free air and rail journeys taken by former politicians and their spouses.

The association is angry that retired MPs and senators will be deprived of a pension increase fully indexed to a pay hike that serving parliamentarians are set to be granted. It also claims that former politicians may have been receiving lower superannuation payments than they were entitled to under law.

Former MPs association president Barry Cunningham said the consequences of a bill being considered by Parliament would be, ''the perpetration by the Remuneration Tribunal of a giant 'con' directly and unfairly detrimental to the welfare of retirees under the 1948 Act''.

The federal government wants to reduce the maximum number of free trips former politicians and their spouses can take under the gold pass scheme from 25 to 10 each financial year. MPs and senators elected at future elections will not be able to qualify for the scheme at all.

Eligible former backbench MPs can claim an annual pension of between 50 and 75 per cent of the base pay of a sitting backbencher.

The Remuneration Tribunal plans to increase backbench MPs salaries from $140,910 to $185,000 and scrap some travel entitlements.

But for the purposes of determining pension increases for former parliamentarians, the tribunal only wants to base determinations on a salary of $146,380.

In a submission to a Senate committee, Mr Cunningham said his association had legal advice that de-linking pension calculations from an MP's full salary could breach the constitutional requirement that property only be acquired under just terms.

''The only logical conclusion is that there is no moral, ethical, or legal justification for any of the Remuneration Tribunal's proposed $45,000 salary increase determination to be 'de-linked from the calculation of the 1948 Act retirees' superannuation'', the former Labor member for the Victorian electorate of McMillan said.

Mr Cunningham also said the reduction of travel entitlements could be found to result in the acquisition of property under the Constitution.

''The association believes this acquisition to be the case, potentially prompting a legal claim for compensation, if this drastic reduction in entitlement is implemented,'' he said.

As a compromise, the association suggested that gold pass return trips be reduced to 17 per year. Or, 10 trips could be made in accordance with existing guidelines and up to 10 more could be taken if the user identified a specific purpose relating to a community benefit.

The Remuneration Tribunal last year put substantial pay rises for MPs and senators on hold until Parliament could pass amendments preventing the changes from boosting superannuation payouts.

Retired Pollies Fight For Perks