Jim Murphy plays the religion card to win votes

• Scottish Secretary Jim Murphy with Pope Benedict XVI, whose visit to this country he is helping to organise. Picture: Complimentary

The speech will focus on the key part "values voters" can play in the forthcoming general election.

Speaking at Westminster to Progress, a Labour think tank, Mr Murphy will say: "In the US, faith has long played a central part in politics – not surprising for a country where 60 per cent of people say that God plays an important part in their lives.

"But it's wrong to think that it plays no role in British politics."

He will tell his audience that research from the time of the 2005 general election suggested Labour support was strongest among religious people.

"Faith voters massively outweigh 'Motorway Men' or 'Worcester Woman', or any other trendy demographic group identified by marketeers," he will say.

"Our lead among them in 2005 needs to be replicated in the coming election – and it will be if we reflect and respect their values and aspirations in our policies, as I believe we should."

The words contrast with the New Labour message under Tony Blair. His communications chief, Alastair Campbell, famously said in office, "We don't do God", while Mr Blair was reticent about discussing his religious faith while prime minister.

Mr Murphy's speech is partly an attempt to stem the tide of Catholic and Muslim voters north of the Border who have switched to the SNP.

In recent years, Labour has seen support drift away following rows over gay adoption and the scrapping of a legislative clause that banned the "promotion" of homosexuality in schools.

Leading Catholic figures, such as Joseph Devine, the Bishop of Motherwell, encouraged churchgoers to seek alternatives to Labour. His attack in 2007 was seen as crucial in a tight Holyrood election, which the SNP won by one seat.

Mr Murphy, a devout Catholic who has been involved with organising this year's papal visit to Scotland, will go further in an effort to reconnect faith values with the traditional aspirations of the Labour Party.

In his speech, the Scottish Secretary will also claim that the Bible gave "the Labour movement the intellectual legitimacy to challenge the old orders".

He will say: "As David said in Psalm 9, 'the Lord is a stronghold for the oppressed, a stronghold in times of trouble'."

He will also quote the words of Labour's founder, Keir Hardie, who proclaimed: "I have said both in writing and on the platform many times that the impetus which drove me first into the Labour movement, and the inspiration which has carried me on it, has been derived more from the teachings of Jesus of Nazareth than from all other sources combined."

Mr Murphy's speech will attempt to challenge the Conservatives, who have recently tried to highlight their support for family values by promising tax breaks to married couples.

"Family is the most important thing in our country," the Scottish Secretary is due to say. "We love our family more than anything else. I am convinced that, like faith, family is another force for good."

But on tax breaks for married couples, he will say: "I celebrate marriage and family life, and while it's wrong for government to financially incentivise one family type over another, I am convinced family is the glue which hold our communities and society together."

However, he will highlight, too, Labour's latest message on "fairness" as being a core religious value. In what many see as a return to "class politics", Labour figures have claimed the Tories are interested only in helping the wealthy few. That message was reinforced by Prime Minister Gordon Brown at the weekend when he unveiled Labour's slogan, "A future fair for all".

Mr Murphy will tell the think tank that fairness is still important in the minds of voters, saying: "I don't buy into theories of fairness fatigue – look at the enormous public response to the Haiti earthquake – but perceptions of fairness at home are shifting."

Mr Murphy's East Renfrewshire constituency has the highest proportion of Jewish voters of any outside London. And some believe his focus on "faith" instead of Christianity is partly motivated by the fight he has with the Conservatives to hold on to his seat.

However, the importance the Scottish Secretary places on the wider influence of religious voters will also be highlighted.

Finally, in an apparent broadside against the Nationalists, Mr Murphy will link patriotism and support for the UK with faith.

"I am also convinced that people, and values voters in particular, are sick of others talking down our country," he will say. "Yes, they know we have problems, but we love our country."

Last night, an SNP spokeswoman said: "People of all faiths and none support the different parties in Scotland, and that forms part of the vibrant political system we have."

Political analyst Professor John Curtice, of Strathclyde University, told The Scotsman last night that appealing to religious values could backfire.

"The Conservatives' appeal to family values has looked outdated and not been very effective," he said. "Also, if you are looking at promoting marriage and other traditional religious values, the evidence is the churches themselves have failed to do just that."

Prof Curtice added: "There is a danger that, by appealing to the religious vote, Mr Murphy could put more people off."