The Labour MP Jim Dobbin, a committed Roman Catholic, has died suddenly at the age of 73 while on a trip to Poland.

Mr Dobbin, MP for Heywood and Middleton in Greater Manchester and a former microbiologist, was travelling with the Council of Europe with his wife Pat, and was in Slupsk when he died.

He was a politician who lived out faithfully the duality, sometimes little understood by the secular world, between Christian socialism on the one hand and strongly traditionalist or "conservative" moral ethics on the other. In 2008, Pope Benedict conferred upon him the highest possible honour for a lay Catholic, making him a Papal Knight of the Order of St Gregory.

He was co-chairman of the All-Party Parliamentary Pro-Life Group. He opposed gay marriage and also took a cautious stance on advances in genetics when they touched on "life" issues.

Pink News noted that Mr Dobbin, who entered Parliament in 1997, was one of 14 Labour MPs to vote against same-sex marriage last year. During his time as an MP he also voted against or abstained on civil partnerships, the Equality Act, the repeal of Section 28, and adoption rights for same-sex couples.

He said of same-sex marriage last year: "I think MPs who voted for this change will rue the day they did so. It is going to have far-reaching ramifications right across British society.

"For example, what sort of effect will this have on generations of children who will now have to be taught that men can marry men as well as women at a young age? A lot of MPs who voted for this did so on a mistaken idea of equality. I am all in favour of equality, but this bill mistook uniformity to mean equality."

He was on Parliament's Involuntary Tranquillizer Addiction Group, the Transport Scrutiny Select Committee and co-chaired the All Party Parliamentary Group for Child Health and Vaccine Preventable Diseases, arguing for more integrated healthcare to combat disease and improve sanitation in the developing world.

He was also Fusilier Lee Rigby's MP, saying after the murder in Woolwich last year that the death had "absolutely traumatised" people in Middleton, Greater Manchester.

His most recent intervention in Parliament was in the debate last week on mitochondrial replacement, which would create what have been dubbed "three-parent babies" or "designer" babies. He quoted Dr David King, director of Human Genetics Alert, as someone "sympathetic to this process" but who "fears that science is racing ahead of ethics. He says that we are in danger of creating designer eugenic babies, and "we do not know where we are going in future."

Referring to scientific tests on the process that have yet to be done and written up, he warned: "Denying Parliament the opportunity to examine these results seems difficult to defend. In effect, it would be asking the House to vote blind on the safety of techniques that the House might reject outright on the basis of the results. Let us be clear and honest about this: the results could not be published and peer reviewed in time for the rumoured vote in the autumn."

Among those who tweeted were Paul Goodman, editor of Conservative Home, who wrote: "A lovely man. Very sad news," and Will Straw, Labour's candidate in Rossendale and Darwen, who said: "Only just caught up with the sad news about Jim Dobbin - he was a very kind & principled man."

Priest and broadcaster Cindy Kent tweeted: "I met Jim Dobbin MP several times and shared Trusteeship with him. Lovely deeply committed Christian. So sad to hear of his sudden death."

He had four children, two daughters and two sons.

Lord Prescott, who was on the Poland trip with him, said: "Jim was an excellent local MP, a strong believer in Europe, a proud Scot and a passionate defender of the NHS. His passing is such a tragic loss and he will be sadly missed by the Labour movement. Jim was a great comrade."

Ed Miliband, the Labour leader, said: "Jim's death is a sad day for parliament. He was a dedicated public servant, representing the people of Rochdale on the council and at Westminster for three decades. A lifelong committed Catholic, Jim always took a lead in fostering links between the Church and the Labour Party, and his strong faith informed every aspect of his political and public life."