By Sarah Toyne BBC News Online personal finance reporter

The UK government could face a legal challenge over its plans to increase National Insurance contributions from next April.

Parity, a group which campaigns for the equal treatment of men and women, says it will seek to challenge the levy, as it says it discriminates against men between 60 and 65 years old.

Unlike men, women over 60 are exempt from paying class one National Insurance contributions, and the group believes that it is unfair that men should be paying for additional investment into the health service.

The Treasury was unavailable for comment on Parity's planned action.

Successful track record

Campaigns by Parity have so far reduced the age at which men can claim free NHS prescriptions, and the winter fuel allowance.

Parity has also had some success through its campaign for free bus passes for men aged 60, and also pushed for a change to the law for widowers benefits, which was introduced last year.

Parity was set up in 1986 as the Campaign for Equal State Pension Ages (CESPA), to campaign principally for men to have the same right as women to a state pension at 60.

It wants to repeal of Section 126 of the Pensions Act, which raises the pension able age of women, to 65 by the year 2020.

David Linsday, legal adviser, said that it believes that the act could be infringing Article 14 of the European Convention on Human Rights, because there is no clause to reduce the retirement age within the act.

Mr Lindsay said that men should have the ability to retire at 60.

"We believe that the absence of any power to alleviate position of men in the meanwhile breaches human rights of men up to 65."

"So many men have to retire for health reasons, but they can't get their pension, " he said.