Key Points:

Helen Clark will have thousands more to spend this Christmas after she and MPs get pay increases today of between 3.8 and 4.1 per cent.

The Remuneration Authority is set to announce the details later today, two weeks before Parliament packs up for the year.

Helen Clark received a 9.4 per cent rise last year, increasing her salary by nearly $30,000 to $347,000. The latest increase will see her salary rise to about $361,000.

This year the Prime Minister's increase will be worth just over $14,000 - paying her $6942 a week to run the country. The average backbencher will get nearly $4500, taking the base salary excluding allowances to about $122,500. All will be backdated to July.

National's John Key has already secured a significant pay rise this week with his election to the leader's job and is on $216,000. That is likely to rise by about $8500.

Since becoming an MP Mr Key, a multi-millionaire, said he has donated roughly the equivalent of his after-tax salary to charity.

He told the Herald this week he planned to continue donating a "significant portion of his new salary" to charity.

Judges are expected today to get a slightly higher increase of just under 5 per cent.

Chief Justice Sian Elias' pay rose 6.5 per cent last year, taking her salary to $348,000 and other judges' pay climbed by up to 4 per cent.

Dame Sian will probably continue to pick up a slightly higher salary than Helen Clark.

The authority is likely to argue that the pay rises reflect general wages and salary movements.

But while ordinary inflation to the year ended September was 3.5 per cent, it is expected to drop to 2.5 per cent - which means MPs are likely to gain a financial benefit from the increase.

The latest data shows pay rises for public servants in the September quarter were on average 5.8 per cent. This was higher than the private sector where the average increase was 5.5 per cent.

The unadjusted labour cost index - considered the best indicator of "take home pay" - shows wage inflation has been running at about 5.1 per cent.

Public Service Association national secretary Richard Wagstaff said wage increases had not been negotiated in a number of public sector agencies, which would bring the average increases down significantly.

"Like politicians, all workers in the public sector should receive at least an annual inflation-related pay increase, to ensure that salaries keep pace with increases in the cost of living."

Cost-of-living increases for those on high salaries involved a lot more money than it did for those on smaller salaries, even if the percentage figures did not look huge.

Workers in areas such as the Government-funded disability sector were paid little more than the minimum wage of $10.25 and needed "a significant pay increase even to meet their basic costs of living".

Engineering, Printing and Manufacturing Union national secretary Andrew Little said the figure was "more or less in line with what we're achieving - 4.25 per cent this year.

"I guess the thing is that they are on reasonably good incomes anyway and it has to be remembered that there are a lot of people who don't get pay rises in any one year. There are a lot of non-union members in particular."