Under the European Union (EU) Gender Directive men will see pension annuity rates fall, while women will see rates rise, according to PricewaterhouseCooper (PWC).
The EU directive, which comes into force on 21 December, will ban the use of gender as a factor in pricing for insurance products and annuities.
According to PWC, male pensioners could see annuity payouts cut by up to £10,000 over the lifetime of the policy.
Raj Mody, head of pensions consulting at PWC, said: “While a small number of women will be better off from the ruling, eight out of ten annuities currently sold in the UK are bought by men, so many more people risk losing out than gaining.
“Women who are beneficiaries of joint life annuities purchased by their male partner will also be affected because they will end up with a lower income.”