It is understood that the Vatican is using its privileged status as a sovereign state to influence the wording of the declaration from the United Nations conference on population to be held in Cairo this September.
The Vatican is bitterly opposed to any UN declaration that will encourage contraception or abortion.
'I understand the position that the Catholic Church, for example, takes on what they describe as artificial methods of birth control. But by the same token, no single group should seek to prevent the Cairo declaration and action plan reflecting the majority view on the importance of everyone having access to adequate reproductive health care,' Lady Chalker told a meeting of population experts in London.
'I have never criticised the Vatican or the Pope. They are perfectly entitled to their views. But I do hope that the Roman Catholic Church in advocating family responsibility will make sure that it gives some help to Roman Catholic couples who want to space their children,' she said.
'I know from too many Catholic missionaries, in Africa particularly, of how torn they are by the Holy Father's teaching and their need to help women who become very borne down by pregnancy after pregnancy.
'Whilst I shan't convince the Vatican, I can at least say let us respect one another's methods, let us not tell other people what to do - we have never sought to do that.'
Lady Chalker will meet Vatican officials next week to try to resolve the issues that are hampering an agreement on the Cairo declaration. 'The block is that there are people in the Vatican who believe that no contraception would ever be right.' In previous meetings, she said, Vatican officials have insisted on calling contraceptives 'alien chemical devices'.
Demographers believe the UN population conference, which is held every 10 years, may be the last opportunity to take concerted international action to try to stabilise the world's population before the end of the next century.
They believe that the 'best case' scenario is for average fertility to decrease with the help of contraception to 1.7 children a woman, which would mean population growth would peak at 7.8 billion, about 1.5 billion more than now, before levelling off at the end of the next century.
The worst-case scenario is for fertility to decline to no more than 2.5 children a woman, leading to a population growth to 19 billion by the year 2100, and to 28 billion by 2150.
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