It came as Labour leader Jeremy Corbyn joined more than 100 other MPs calling on the Home Secretary to ban pro-life vigils outside abortion clinics.

A letter, signed by 113 MPs including Corbyn and Vince Cable, the leader of the Liberal Democrats, was sent to coincide with the anniversary that first permitted abortions in Britain.

It comes after Ealing council in West London voted to ban a vigil outside a local clinic in the borough.

Rupee Huq, Labour MP for Ealing Central, said the idea was 'not to stop protests, but to ask protesters to instead make use of the many places they could protest -- from Parliament Square to town centres to Speaker's Corner'.

The letter read: 'The women accessing clinics are not seeking debate -- they are trying to make their own personal decision about their own pregnancy.'

But Lord Alton of Liverpool, a Catholic peer in the House of Lords, described the consequences of the law 50 years ago as a 'tragic, industrialised destruction of human life'.

Conservative MP Ann Widdecombe called for church bells to toll over the weekend to commemorate the anniversary and other MPs, peers and lobby groups will gather again on Saturday in Westminster for a prayer vigil and to 'redouble efforts to prevent further liberalisation of abortion'.

Writing in the Catholic Herald Lord Alton said: 'The medical profession has been subverted, with the Hippocratic Oath quietly dropped from medical courses because of its explicit condemnation of abortion. Preferment in gynaecology and obstetrics has become virtually impossible for those who refuse to comply.'

He added: 'But as the scales are falling from people's eyes, the tide of history is turning; and, looking to the future, these heart and head arguments are slowly changing minds.'

It comes as Scotland's chief medical office wrote to health boards to say abortion pills can be taken by women at home, meaning abortions will be available outside a clinical setting for the first time in the UK.

Alongside the prayer vigils graphic images of aborted foetuses dominated Parliament Square as Abort67, a pro-life campaign group, said the reality of terminations needed to be revealed.

Ruth Rawlins, head of Abort67, told Christian Today abortion was hidden.

'We find as we show the horrific reality of abortion -- and yes it is horrific -- people are seeing the reality of this decision. It's not a choice about a medical procedure but the choice to kill an innocent human being. That changes everything.

'Our intention is not to upset women but we do know that that could be the reality of seeing these images. Our primary intention is to change minds,' she said.

'While we care about feelings we believe that lives are more important than feelings at the end of the day.'

But Vicky [not her real name], a tourist from Canada, told Christian Today she found the images personally offensive.

'Women have abortions for all different kinds of reasons,' she said. 'I think this is really inappropriate.