Sweeping changes to the rules governing pensions which come into force tomorrow will affect nearly everyone who is saving for their retirement, financial advisers claim.

But despite the potential impact the changes could have on people, the majority of consumers have failed to review their retirement saving ahead of A-Day.

Recent research carried out by Brewin Dolphin Securities found that 58 per cent of people with a pension were not aware that the new rules could affect them, while just 32 per cent of people who knew about the changes had reviewed their pension.

In reality, most people on average incomes are unlikely to feel the impact of A-Day until they approach retirement.

While the new rules will enable people to pay more into a pension each year - up to 100 per cent of their earnings capped at #215,000 this year - very few people are likely to take advantage of this, as only a minority currently make the maximum contribution.

The new #1.5 million lifetime limit on pensions saving is also unlikely to be a problem for the vast majority, although financial advisers have warned that if the allowance fails to rise in line with inflation, it could catch out middle earners in years to come.

People who think their pension fund may exceed the limit in future need to take action within the next three years to protect their benefits.

There are two types of protection, primary protection and enhanced protection, both of which are highly complex and people considering applying for them should talk to a financial adviser.

People are more likely to feel the benefits of A-Day when they retire, as under the new rules they will be able to continue working for their current company while also drawing a pension from that firm, enabling them to take a more flexible approach to retirement.

They are also more likely to be able to take up to 25 per cent of their pension as a tax-free lump sum, and they will have a bigger choice in the types of annuity they can buy with their fund.

On the downside the minimum age at which people can retire will be increased from 50 to 55 by 2010.

People who can currently take more than 25 per cent of their pension as a tax-free lump sum can continue to do so after A-Day, but they must make sure their scheme trustees have records showing they are entitled to this.

The immediate impact of the changes will be more obvious to companies that provide occupational schemes and insurers offering pensions because the new simplified rules will reduce the burden of administration on them.

But it is likely that there will be some problems follow-ing the changeover as companies adapt their computer systems to comply with the new rules.

A spokesman for the Association of British Insurers said: "Quite clearly in order for companies to facilitate all these changes they need to amend all their systems for data collection and data processing.

"They also need to know the precise details of changes."

He said the only place these details could come from was HM Revenue & Customs, but in a number of cases it had been very slow to pass on the information to insurance companies, and some details were still not known, while others were only announced in the Budget.

As a result he said some systems upgrades could be delayed, which could lead to delays for consumers.

But he played down fears that people's pensions could be paid late, saying it wasn't going to lead to "chaos and confusion", although he added that it could result in some inconvenience for customers as companies may temporarily have to rely on manual systems.

Of course, none of this is going to do much to help with the pensions crisis of closing and frozen company schemes and a general loss of confidence in the whole structure.

Robin Ellison, head of strategic development at Birmingham law firm Pinsent Masons, and currently chair-man of the National Association of Pension Funds, said: "There has never been so much pension legislation, all of it well-intentioned.

"The array of acts of Government, statutory instruments, guidance notes and codes of practice however makes a mockery of the public policy intention to simplify the system.

"It is no longer possible even for experts, never mind members of the public, to have an understanding of the details of the pensions system. We are in danger of having the best regulated pensions systems in the world - with the fewest number of pension arrangements to regulate.

"Fortunately there are now signs that the regulators are beginning to understand the counter-productiveness of this regulatory framework."

However there are some rays of light at the end of the tunnel.

According to Aon Consulting, FRS17 funding deficits for UK pension schemes have been reduced by around 35 per cent to their lowest levels for over three years.

The total estimated deficit for the 200 schemes in Aon's survey was #48 billion at the end of March, compared with #72 billion at the end of 2005.

It said this was down to a return on UK equities of almost four per cent and a rise of around 0.3 per cent in long-dated bond yields.

Accountants Deloitte estimated pension fund deficits at Britain's top 100 listed companies stood at #60 billion.