Dumped ACT Liberal Gary Humphries should be entitled to a lifelong pension of about $80,000 a year when he leaves the Senate in September.
Senator Humphries has been in Federal Parliament for 10 years.
He is facing involuntary retirement after being defeated by Zed Seselja in a preselection ballot at the weekend to be the Liberal Party's prime Senate candidate.
He says he remains angry about the process used to replace him for the Senate race.
But he will not contest any further preselection process.
Senator Humphries said on Monday he believed the result would have been different had many of his supporters not been denied a vote.
Mr Seselja said on Monday he would resign as a member of the Legislative Assembly before the ''election period'' begins for the federal poll in September.
He is expected to take a pay cut when he replaces Senator Humphries in Parliament.
As ACT Opposition Leader Mr Seselja earned about $213,000, a figure made up of the $125,259 base salary for MLAs and the Opposition Leader's allowance of $87,681.
He has already lost the allowance after resigning as Opposition Leader.
Senator Humphries was a member of the Legislative Assembly for 14 years, including as chief minister.
He entered the Senate in 2003 on a casual vacancy created by the resignation of long-serving Liberal senator Margaret Reid.
The Finance Department says the minimum pension rate for former federal members of Parliament is 50 per cent of the ''parliamentary allowance''.
Each additional year of service attracts an additional pension of 2.5 per cent.
The ''parliamentary allowance'' is the base salary less a portion as determined by the tribunal.
Parliamentarians who become entitled to a pension may convert half to a lump sum.
The base salary of a federal MP is $190,550 along with extra benefits including electorate and travel allowances, but the Remuneration Tribunal has determined that a portion - $39,770 - will not count for superannuation calculations.
''His/her notional salary for superannuation purposes is $150,780,'' it says.
Superannuation for parliamentarians is more generous than for other workers due to what political leaders say is the lack of security in their jobs.
Mr Seselja dismisses as a ''disaffected rump'' those forces within the Liberal Party that have launched
action that could lead to his preselection victory being overturned.
However, Senator Humphries, no longer on friendly terms with his former protege, said the preselection process was badly flawed. ''Flawed or not, the party has spoken and it's time for me to move on … .
''I was angry that I thought there were things very seriously wrong with the preselection process. On Saturday itself a large number of people arrived to vote, having been informed that they were preselectors, and were told without any warning that they weren't preselectors.
''People who'd been members of the party for accumulatively centuries - centuries of party membership was knocked back through that process. I don't understand why.''
Late on Monday Mr Seselja said federal Opposition Leader Tony Abbott had still not talked to him about his preselection win. He said he respected the federal Liberal leader's loyalty to Senator Humphries.
''He backed the guy on his team,'' Mr Seselja said. ''My entire parliamentary party backed me. We sometimes see these kind of things happening.
''In the end, the branch members have made a decision. I know that Tony will respect that.''