In July pensions minister Steve Webb said he would use the Pensions Bill to reform the amount of state pension people receive if they defer taking their benefit.
Under existing legislation workers who delay taking their state pension receive 10% uplift in payment for every year they delay, this is set to fall to 5%.
At present, a worker who defers for one year, can expect an additional £579 in their annual state pension, for someone who delays for five years, this rises to £2,893.
The study found people who delay taking their state pension by five years would be nearly £29,000 worse off under the new reforms.
Chris Noon, partner at Hymans Robertson, said: "If the benefit of deferring state pension falls to 5% then a large percentage of these people will choose to take their pension as soon as they are eligible.
"Given the significance of state pension to overall Government finances this may not be good news for the national deficit."
The study found under the current system, those people entitled to the basic state pension of £107pw who defer taking their benefits by just a year could expect to receive an additional £579 for the remainder of their retirement.
Over twenty years the value of deferring for just twelve months adds up to £11,575.
If the uplift falls to 5% the equivalent benefit falls to £289 and pensioners could lose out on £5,782 over twenty years. The comparable loss for five years deferral is £28,933, the study found.
Noon added: "The danger of reforming deferral now is by the time changes come into force, interest rates may be on the rise again and the state pension may lose some of its value for those who can afford to delay taking it."
