AgeUK-organised protest is against plans to raise state pension age more quickly, meaning thousands of women will need to work for longer or face loss of retirement income

Politicians came under siege as hundreds of women gathered at parliament to protest at plans to increase the state pension age more quickly.

The protest, organised by charity AgeUK, coincided with the second reading of the pensions bill, which included a revised timetable for changes to the state pension age.

The bill will bring forward the raising of women's state pension age to 65 by two years, from 2020 to 2018, followed by a further increase to 66 for both men and women by 2020 – six years earlier than planned by the previous government.

The women, most of whom will be in their 50s and face working between one and two years more than previously expected, want meetings with their constituency MPs to express their disapproval. Rachel Reeves, shadow minister for pensions, and Barbara Bates, a 57-year-old shop worker from Durham, planned to hand in a petition signed by more than 10,000 people to Downing Street. Women have deluged MPs with letters complaining that the revised timetable will not allow them to prepare financially for the changes.

Research by AgeUK indicates that 40 MPs have good cause to be worried about antagonising potential female voters: the number of affected women in their constituencies outstrips their majority. They include 19 Conservative MPs, 16 Labour MPs and five Liberal Democrat MPs.

The 10 most at risk include seven women MPs – Nicola Blackwood (Conservative, Oxford West and Abingdon); Jackie Doyle-Price (Conservative, Thurrock), Glenda Jackson (Labour, Hampstead and Kilburn), Lorely Burt (Liberal Democrat, Solihull), Gloria De Piero (Labour, Ashfield), Julie Hilling (Labour, Bolton West), and Annette Brooke (Liberal Democrat, Mid Dorset and North Poole) – and three men – Matthew Offord (Conservative, Hendon), George Eustice (Conservative, Camborne and Redruth) and Mark Spencer (Conservative, Sherwood).

Annette Brooke, who has 1,400 female constituents who will be affected by the proposed changes, spoke against the changes at a debate in Westminster Hall last week.

She said: "Historically women have often suffered injustices in the pensions system. Whenever you have a sharp cut-off date there is an injustice. The proposed reforms will mean that women born between 1953 and 1954 will be caught out. However, it is not too late to have another look at these reforms, to ensure that once again women, and this age group in particular, do not disproportionally lose out. It is not fair to keep moving the goalposts as people get older.

"We know this is not about a large number of people, so money could be found by the coalition government. We need to know how much it would cost to even out matters. This is an opportunity for the coalition to say, 'We really do care about giving equal treatment to the citizens of this country.'"

Revisions to the timetable will affect nearly 5 million people, of which 500,000 are women who will have to work at least one year more, while 33,000 will have to work two years longer. It will cost the worst affected women up to £10,000 each in lost pension income, and will force both men and women to wait longer for vital benefits such as pension credit which are paid in line with the state pension age.

Ros Altmann, director general of Saga, says unemployment benefit will not be an option for many of those affected.

"Out of work benefits will last only six months and are far less than state pension. Having a small private pension will exclude many of these women from benefits and many would not want to claim anyway. They feel this is an insult," she said.

AgeUK says those from poor backgrounds who are more reliant on the state pension, and disabled people, are expected to suffer most if the bill goes through unchanged.