The Harper government has moved to preclude disgraced senators Mike Duffy, Pamela Wallin and Patrick Brazeau from the parliamentary pension plan while they are under suspension from the upper house.

Amendments to the Members of Parliament Retiring Allowances Act are included in a 375-page omnibus budget implementation bill introduced today in the House of Commons.

The move is aimed at ensuring the trio don't accrue pensionable service while under suspension for making allegedly fraudulent expense claims.

The three were suspended without pay last November for the duration of the parliamentary sitting, which is expected to continue until 2015 — the same year all three would ordinarily become eligible to collect a generous parliamentary pension.

Changes not retroactive

The government was embarrassed to discover, after the fact, that the trio's time in political purgatory would legally count towards the six years of service needed to qualify for a pension.

The change will not apply retroactively to the moment the three were suspended last fall but it will apply to them going forward once the amendments are enacted.

There was no immediate comment from lawyers for any of the three suspended senators.

But Wallin's lawyer, Terrence O'Sullivan, has in the past argued that the suspensions would be invalidated if the government were to retroactively change the pension rules.

Changing the rules, after the fact, would mean senators did not make an informed choice about the fate of their colleagues when they voted to suspend them, he has said.

O'Sullivan has threatened to take the matter to court.