Speaking to BBC News, Ms Welch said: "It is 100 percent discrimination, there is no doubt about it and we are actively considering an appeal.

"We have submitted grave and systemic evidence to the CEDAW committee in Geneva and they're looking at making an inquiry into the way that they've treated 1950s women."

She added: "We've also got the people's tribunal which is going to be looking at discrimination against all women and girls.

"What we're going to do there is write up draft legislation to bring a women's bill of rights into domestic law. It's not over."

READ MORE: State pension shock: 75% of 1950s weren't told about age change

Julie Delve, 62, and Karen Glynn, 63 - supported by campaign group BackTo60 - brought a Court of Appeal challenge over the changes after losing a landmark High Court fight against the Department for Work and Pensions (DWP) last year.

The women argued that raising their pension age unlawfully discriminated against them on the grounds of age and sex, and that they were not given adequate notice of the changes.

But in a judgment published on Tuesday, Master of the Rolls Sir Terence Etherton, Lord Justice Underhill and Lady Justice Rose unanimously dismissed the women's claim.

They found that introducing the same state pension age for men and women did not amount to unlawful discrimination under EU or human rights laws.

As part of their ruling, the senior justices said that "despite the sympathy that we, like the members of the Divisional Court (High Court), feel for the appellants and other women in their position, we are satisfied that this is not a case where the court can interfere with the decisions taken through the Parliamentary process".

They said that "in the light of the extensive evidence" put forward by the Government, they agreed with the High Court's assessment that "it is impossible to say that the Government's decision to strike the balance where it did between the need to put state pension provision on a sustainable footing and the recognition of the hardship that could result for those affected by the changes was manifest without reasonable foundation (MWRF)".

Following the ruling, Ms Welch, founder of the BackTo60 campaign, said the group's legal team is "actively looking" at taking the case to the Supreme Court.

She also told the PA news agency "this isn't over by any means".

DON'T MISS

State pension warning: Boris Johnson under pressure in age change row [INSIGHT]
State pension: 1950s women not allowed to pay into pensions [VIDEO]
State pension: 'Men had freebies!' Campaigner says men had free NI [ANALYSIS]

Ms Welch, who described the decision as "unconscionable", said there is "no doubt in our minds that it's discrimination".

She also said that separately, BackTo60 is involved in contributing to work under the Committee on the Elimination of Discrimination Against Women (CEDAW), an international treaty.

A DWP spokesperson welcomed the ruling, saying: "Both the High Court and Court of Appeal have supported the actions of the DWP, under successive governments dating back to 1995, finding we acted entirely lawfully and did not discriminate on any grounds.

"The claimants argued that they were not given adequate notice of the changes to state pension age. We are pleased the court decided that due notice was given and the claimants' arguments must fail."