Margaret Curran, the Labour candidate in the Glasgow East by-election, pledged yesterday to support the Government's controversial Human Fertilisation and Embryology Bill, if she becomes an MP.

Her support came despite a withering attack on Labour over the issue by Bishop Joseph Devine, the second most senior Catholic churchman in Scotland, whose diocese covers the constituency.

The bishop accused Labour of

“violating moral law” and “losing ethical credibility”, adding that Labour had lost the electorate's trust and could no longer take Catholic support for granted.

Ms Curran's stance is sure to make the issue a clear dividing line between the two front-runners for the seat, which has a large Roman Catholic population - about a third of the electorate of 62,000.

Labour has been accused of postponing a vote on the Bill this week until the autumn to avoid offending Catholic voters ahead of the by-election.

Ms Curran detailed her position on the Bill during a televised debate on the BBC's The Politics Show yesterday between the four main party candidates. “I do think morals and ethics are important, obviously I wouldn't agree with him [Bishop Devine]. I have followed the debate; I would vote with the Government,” she said.

SNP policy is for a free vote on the Bill, but John Mason, the Nationalist candidate, said that he would vote against it if elected.

Mr Mason, a Baptist, said: “Coming from a faith community background I assume we should not be doing that kind of research and think there are other ways of dealing with that.”

Ms Curran's campaign was dealt a blow after Bishop Devine's attack in letter to Labour MPs in Scotland in which he said that Labour “had broken its pact with Christian voters”.

The bishop's remarks could not have come at a worse time for Labour as it battles to defend Glasgow East.

Although Ms Curran backed the Government on the Embryo Bill she criticised Alistair Darling, the Chancellor, over planned rises in car tax.

Ms Curran said last week that if elected, she would bring Mr Darling to Glasgow East to hear the concerns of ordinary voters away from the media spotlight.

But she said during the TV debate: “I think he should reduce the vehicle excise duty.” She went on: “Alistair Darling is welcome to come to the constituency at any other point, but my point was that at this particular period there has been a shift in economic circumstances.

“I have met Alistair Darling many times and he is very welcome in the constituency.”

The SNP said later: “No wonder Margaret Curran doesn't want Alistair Darling to come to Glasgow East - she just dumped the Chancellor on the car tax. It is extraordinary that Margaret Curran thinks the Chancellor should come to Glasgow East at ‘any other point' but not during a crucial by-election when his policies are causing so much pain.

The debate came against the backdrop of the first opinion poll to be taken during the campaign, which revealed that Labour is on course to hold the seat.

The ICM poll for the Sunday Telegraph and the Sunday Mirror put Labour on 47 per cent, 14 points clear of the SNP on 33 per cent. The 14-point gap will come as a huge relief to Gordon Brown, who would face a backlash if Labour lost its 25th safest seat in the UK. The poll showed a swing of 15 per cent from Labour to the SNP but was well short of the 22 per cent needed by the Nationalists to overturn Labour's 13,507 majority.

Labour said that the figures showed there was still “strong support” for the party but the SNP argued its candidate was two thirds of the way to victory and had made huge inroads into the 45-point lead Labour had at the last general election.

Alex Salmond, the SNP leader, said that an opinion poll published three days before the Govan by-election that the SNP won in 1988 had put the party 20 points behind Labour.

“With ten days to go the SNP is closing the gap in Glasgow East and is on course for the political earthquake that will send shockwaves around Westminster,” the First Minister said. “After one week of the campaign the SNP is two thirds of the way to a sensational by-election win.”

By contrast Labour gave a low key reaction to the poll. David Cairns, the Scotland Office Minister, said: “Unlike Alex Salmond, we're not going to be smug about one poll.”

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