The SNP has challenged the Prime Minister to act to help those women, born in the 1950s, affected by pension equalisation.

SNP Westminster Group Leader Angus Robertson called on David Cameron to respect a Parliamentary decision to immediately introduce transitional arrangements for those women negatively impacted.

Speaking during Prime Minister's Questions, the MP for Moray asked: "Does the Prime Minister agree that there is no justification for discrimination or unfairness towards women in the private sector, public sector or by Government?"

But Mr Cameron said, in raising the retirement age, the Government "made the decision that no one should suffer a greater than an 18 month increase in their retirement age".

The introduction of the single tier pension he added would be "one of the best ways we can end discrimination in the pensions system because so many women retiring will get so much more in their pension".

Mr Cameron replied: "In terms of wanting to end discrimination against women in the public sector, in the private sector, in politics, in this place, yes absolutely."

Plans to increase the state pension age for women from 60 to 65 between 2010 and 2020 were initially set out in 1995.

But the coalition government decided to speed up the process in 2011, resulting in the state pension age for women due to increase to 65 in November 2018 and then to 66 by October 2020.

Campaigners argue the women affected have had to rethink their retirement plans at relatively short notice and suffered "undue hardship".

Earlier this month MPs overwhelmingly backed a parliamentary motion which urged the Government to immediately introduce further transitional arrangements for those women negatively affected by the changes. But the vote was non-binding and does not compel ministers to act.

Mr Robertson used both his party's questions during PMQs to press the Prime Minister on the issue of pensions.

He asked: "He's aware of the state pension inequality that is impacting on many women and that this Parliament voted unanimously for the Government to and I quote 'immediately introduce transitional arrangements for those women negatively affected by pension equalisation'.

"What is the Prime Minister going to do to respect the decision of this Parliament and help those women who are affected, those who are born in the 1950s and should have had proper notice to plan their finances and their retirement."

Mr Cameron replied: "Well what I'd say to him, first of all the equalisation of the retirement age came about on the basis of equality which was a judgment by the European Court that we put in place in the 1990s.

"When this Government decided, rightly in my view, to raise the retirement age, we made the decision that no one should suffer a greater than an 18 month increase in their retirement age and that's the decision that this House of Commons took."

He added: "In terms of ending discrimination in the pensions system, I would say that the introduction of the single tier pension at £155 a week will be one of the best ways we can end discrimination in the pensions system because so many women retiring will get so much more in their pension, which of course under this Government is triple lock protected, so they'll get inflation, earnings or 2.5% and never again the derisory 75p increase in the pension."