A leading Roman Catholic leader in Scotland has attacked the Labour party over its support for the Human Fertilisation and Embryology Bill.

Bishop Jim Devine’s attack comes as the Glasgow East constituency is in the middle of a by-election that is critical for Labour.

“Christian people have not changed. It is Labour that has broken its pack with Christian voters,” he wrote in a letter to all MPs representing Scottish constituencies.

“What are we to do when our religion is attacked and our conscience outraged?

“When one considers the self-inflicted injuries this Labour Government has visited upon itself, one could be forgiven for thinking it had some kind of death wish.”

The government won a vote on the Bill in the Commons in May. It approved human-animal embryos for the harvesting of stem cells. They must be destroyed after 14 days.

MPs were given a free vote on several clauses and three Roman Catholic cabinet ministers, Ruth Kelly, Des Browne and Paul Murphy, voted against the government.

The Commons also approved the creation of so-called ‘saviour siblings’ and proposals that will allow lesbians and single heterosexual women equal access to IVF and fertility treatments.

MPs rejected a reduction in the time limit for abortion.

Devine, who is Bishop of Motherwell, said that Labour had “lost its ethical credibility in the nation at large” as a result of these votes.

One third of the electorate in Glasgow East are Roman Catholic according to census data.

However, Labour’s candidate in the by-election, MSP Rosemary Curran, said she would have supported the Bill, will support it if elected and is not convinced of the need to change abortion.

Labour won Glasgow East in 2005 with a 13,500 majority and it would be seen as another blow to Gordon Brown if the seat fell to the Scottish National Party.

SNP candidate John Mason said he would vote to lower the time limit for abortions and was “uncomfortable” about some of the other measures in the Bill.

Bishop Devine attempted to interfere in the democratic process during last year’s elections for the Scottish parliament by publicly withdrawing his backing from the Labour party.

In March he claimed that the “gay lobby” attends Holocaust memorials “to create for themselves the image of a group of people under persecution.”

The bishop said there is a “giant conspiracy” going on and claimed he is taking on the forces of secularism.

“The homosexual lobby has been extremely effective in aligning itself with minority groups.

“It is ever present at the service each year for the Holocaust memorial, as if to create for themselves the image of a group of people under persecution.”

He criticised the decision to honour Sir Ian McKellen for his work for equality, pointing out that Oscar Wilde was jailed for homosexual offences.

He also took the opportunity to give advice to parents of gay children.

“This must be a nightmare moment for any parent,” he said.

“I would try to handle it with a degree of compassion.

“But I would not tolerate that kind of behaviour. I would not condemn but I would not tolerate it.”

Between 5,000 and 15,000 gay men were held in concentration camps by the Nazis as members of an “anti-social group.”

Historians estimate that 60% of them died while incarcerated.

Last year Bishop Devine said he would close the Roman Catholic adoption agencies rather than help same-sex couples to adopt children.

The Human Fertilisation and Embryology Bill is expected to complete its final parliamentary stages after the summer recess.