My hon. Friend Colin Challen has done well to secure a debate on equal pension provision for service personnel, regardless of when they served in Her Majesty's armed forces. Although the subject of British armed forces pensions has a long history that stretches back to the time of Elizabeth I, it is better that I start nearer the present day.

In the early 1970s, the Ministry of Defence introduced an armed forces pension scheme following the introduction of the military salary in 1970, which replaced the system of basic pay and allowances. The military salary meant that the MOD could link pensions to pay for the first time, and in April 1972, representative pay rates were introduced on which pensions for members of the armed forces pension scheme were based. That meant that under that scheme, members of the armed forces with the same rank and same number of years' reckonable service were awarded the same pension, regardless of their actual pay on leaving service. Those pension arrangements are actually made up of three separate schemes that were established under a range of prerogative and statutory powers. The current arrangements are found in the Naval and Marine Pay and Pensions (Non-Effective Benefits and Family Pensions) Order 2001, the army Pensions Warrant 1977 and the Queen's regulations for the Royal Air Force. The enabling legislative powers are to be found respectively in the Naval and Marine Pay and Pensions Act 1865, the Pensions and Yeomanry Pay Act 1884 and the Air Force (Constitution) Act 1917.

In the early 1970s, members of the schemes were awarded a pension only if they had completed at least 16 years' reckonable service as an officer, or 22 years' reckonable service in another rank. Engagements for shorter periods were on non-pensionable terms. However, gratuities were awarded to those who left without qualifying for a pension, but who had completed nine years' reckonable service as an officer, or 12 years' reckonable service in another rank. The definition of reckonable service is all paid service after the age of 21 for officers, or after the age of 18 for other ranks.

Before the introduction of the Social Security Act 1973, there were no rights to preserved pensions in any public or private pension schemes. Most schemes had very restricted qualifying criteria for the award of pensions. For instance, to qualify for a pension under the civil service arrangements, an individual had to be over 50 and to have served for 10 or more years. Individuals who left voluntarily before meeting both these criteria lost their rights to pensions. The 1973 Act brought about changes by requiring all pension schemes to preserve pension rights for those who left service after 6 April 1975 and had completed at least five years' qualifying service and attained the age of 26. Subsequent Social Security Acts reduced the qualifying period from five years to two years and removed the age qualification requirement. The armed forces pension scheme incorporated those changes from the operative date of 6 April 1975. It is for that reason, and to differentiate that scheme from the new pension scheme introduced in 2005, that we now call the scheme AFPS 75.

As my hon. Friend said, those changes were not retrospective. It is a legal principle that individuals receive benefits in accordance with the scheme rules that were in place at the time of their retirement. It is a principle of public service pensions policy, and one that has been upheld by successive Governments, that improvements to pension schemes are not made retrospective. If the changes were made retrospective, it would add significantly to the cost to the taxpayer, not least because the issue is common to other public service schemes, not just that for the armed forces.

My hon. Friend asks me to distinguish between members of the armed forces and others who serve as public servants, such as teachers and members of the emergency services, but that would be a legally untenable position. He also asked me to estimate the costs involved. We have not made a specific estimate of the cost of backdating armed forces preserved pensions to prior to 1975, and my hon. Friend alluded to some of the difficulties that would prevent us from achieving that.

We have made a general examination, and the numbers affected are very large, so the costs, whether for the armed forces or more widely, would be considerable and would run into billions of pounds. I fully recognise that a number of individuals who have no occupational pension rights for their time in the armed forces—

It being Seven o'clock, the motion for the Adjournment of the House lapsed, without Question put.

Motion made, and Question proposed, That this House do now adjourn. —[Mr. Alan Campbell.]