Speaking at a Mass in the Crypt of the House of Commons, the Cardinal will remind MPs and Members of the House of Lords of the "time of confusion" in which we live and the need for legislators to follow their conscience, even at the expense of political difficulty.

The Cardinal will note: "It has struck me that for all the Church's calls for recognition of the inviolability of conscience the sad reality is that the vast majority of politicians have given support to various attacks on human life with apparent lack of reproach from conscience.

"What does one say then, in the face of those who without guilt condemn the innocent in the womb, show disregard for family life and play God with the building blocks of life?"

The Cardinal will also state: "We cannot but help notice that consciences among even some who ostensibly see themselves as loyal Catholics or champions of the life have been dulled even so far as to acquiesce with what is euphemistically called a right to choose."

Quoting St Paul, the Cardinal will tell politicians: "God's gift was not a spirit of timidity, but the Spirit of power, and love, and self-control. So you are never to be ashamed of witnessing to the Lord".

"That is precisely what all involved in political life are called upon to do at this present time."