Former prime ministers and their spouses are collecting tens of thousands of dollars in perks – and a new bill being led by Prime Minister John Key will lock them in.

Figures obtained by the Sunday Star-Times show former prime ministers such as Helen Clark and Jim Bolger collect near the national average wage each year in annuities, and pocketed annual increases of up to 4.75 per cent on their benefits.

On top of annuities, eight former prime ministers or their spouses have also spent more than $330,000 of taxpayer money on travel over the past three years.

The benefits date back to the recommendations of a royal commission that reported nearly 50 years ago.

Rather than being scrapped, however, a bill being led by Key will lock them in place. Key's Members of Parliament (Remuneration and Services) Bill includes changes to the way MPs and ministers are given entitlements. Instead of the Speaker deciding on MPs' travel and accommodation allowances, most tasks will go to the Remuneration Authority.

But entitlements for former prime ministers who have served at least two years will not change.

Key's bill specifically legislates for former prime ministers who had the job for longer than two years to be paid at a rate according to their length of service up to five years. The annuity would be paid until their death and then to a surviving spouse or partner, even if they remarried. The same rules would apply to travel entitlements.

Clark, who now works as the third-ranked United Nations official, receives the same annuities as Bolger. Spouses of the late Sir Robert Muldoon and David Lange are entitled to half the annuity paid to Clark and Bolger.

Even the spouse of Bill Rowling, PM for 15 months, has spent $14,802 on travel in three years.

Lange's widow, Margaret Pope, said that as a backbench MP, Lange had argued the annuity should be suspended while a former prime minister was collecting income from the public purse but nothing came of his request.

"The annuity belongs to a time when prime ministers didn't have careers after politics and their spouses weren't in paid employment," Pope said.

"It has been a great help to me – it was a blessing when David was too ill to work regularly – but I could not put up a defence of it."

Key, a millionaire former currency trader, will not say if he will take the annuity when he leaves office. His spokeswoman said the annuity "recognised the service former prime ministers gave their country" and that their obligations continued "to an extent".

A 2010 Law Commission review recommended annuities should stay; travel entitlements should be capped; and entitlements should be publicly disclosed each year.

Key's spokeswoman said he agreed that "the unrestricted nature of these entitlements contrasts with current trends towards greater restraint and accountability in the use of public money". The bill would leave it up to the Remuneration Authority to decide on entitlements in future, however.

Key's bill is before select committee and submissions close on May 18.

THE NUMBERS (2009-2012)

ANNUITIES

Sir Robert Muldoon (spouse) $65,515

David Lange (spouse) $65,515

Jim Bolger $131,030

Dame Jenny Shipley $52,412

Helen Clark $131,030 TOTAL: $445,502

TRAVEL

Bill Rowling (spouse) $14,802

Sir Robert Muldoon (spouse) $4313

David Lange (spouse) $4855

Geoffrey Palmer $42,772

Mike Moore $32,916

Jim Bolger $114,442

Dame Jenny Shipley $55,518

Helen Clark $60,487

TOTAL: $330,105

GRAND TOTAL: $775,607