One in five workers (19%) in the UK expects that they will never be able to afford to retire fully, according to a study published this week by HSBC.

However, other research shows a growing proportion of people are working beyond retirement age because they actually want to. For both groups working longer is easier nowadays because most employers can no longer insist that employees retire at a pre-determined age.

Over the past 20 years, the average age at which people stop working has risen by nearly two years according to Government statistics. Women are most likely to work beyond their state pension age. Latest figures show that the average age at which men withdraw from the labour market has risen from 63.1 in 1993 to almost 65 (64.8) today, while women are now working on average until the age of 62.6 - up from 60.9 in 1993.

Some firms are well known for their employment of older people. At B&Q approximately a quarter of the workforce is over 50, and the oldest employee is 96. Asda is another example of a firm which actively recruits older employees.

The UK Government has been trying to encourage more firms to provide employment for this age group and pointed out recently that McDonalds had reported 20% higher performance in outlets employing workers over the age of 60.

The Future of Retirement study published this week found that one in five Britons expected they would never stop working. Most expected to remain employees. Only 7% of those questioned in the UK said they intended to start a business in retirement (compared to 27% globally).

HSBC recommends people not to rush into retirement. Its research found that nearly two-thirds (64%) of those who entered semi-retirement wished that they had stayed longer in full time employment. Their regrets were largely for positive reasons, with many retired people seeing work as an important means of keeping the body and mind active.

Prudential's latest retirement study also found that more people were considering working past state retirement age. Nearly three in five (57%) people due to retire this year said they were considering working either full or part-time.

This compared with 40% in 2012. More than half (55%) wanted to extend their careers to keep their mind and body healthy compared to 40% looking to boost their incomes.

Changes in employment law mean that since 2011 employers have no longer been able to force employees to retire at a pre-set retirement age, unless they can clearly justify it.

"Most employees can now work as long as they want to. If they are asked to stop working just because they have reached a certain age, this could be considered age discrimination and they can take their employer to an employment tribunal.

However, some financial conditions may change if you work beyond your firm's normal retirement age. If you belong to a final salary scheme, continuing as a member may be difficult.

Stan Russell, retirement income specialist at Prudential, said "This will depend on the scheme rules. It may not be open to older members. Final salary pension schemes are not particularly flexible."

However, if the firm has a money purchase scheme based on contributions, or there is such a scheme for new employees, you should be able to continue to accrue pension benefits.

You may have other benefits associated with your job. Tom McPhail, pensions specialist at Hargreaves Lansdown says "If you have received other benefits such as life insurance, income protection and private medical insurance, you should expect to continue receiving them. If not, you should challenge your employer."

One of the advantages if you work past state retirement age is that you will no longer have to pay National Insurance contributions so check that your employer is not still deducting them from your pay.

However, they will still have to make the employer's contribution.

Rather than stay with an existing employer many people decide to switch jobs according to the Prudential's Stan Russell.

He said "They decide they want to downsize their working hours, and maybe switch to doing something different for the last five or six years of their working lives, maybe something they have always wanted to do but haven't been able to previously."

Richard Wadsworth of financial advisers Carbon Financial in Glasgow, says "Our clients, who have been working long hours and long weeks, often find it difficult to switch off when they get to retirement so they like to take on some smaller roles in fields related to the industry they have been working and also do some voluntary work too, and then gradually wind down in their late 60s"

Soon most people won't have any choice about working beyond the current state pension ages.

From December 2018 the state pension age for both men and women will start to increase to reach 66 in October 2020 and from there to 67 between 2026 and 2028.