Shadow Education Secretary Tristram Hunt has insisted he meant “no offence to nuns” after appearing to suggest they do not make good teachers.
Responding to journalist Christina Odone’s claim on Question Time that her most inspiring teachers had not been to training colleges, Mr Hunt said “these were all nuns, weren’t they?”
Ms Odone told the Catholic Herald his comments were “arrogant and ignorant”.
But the MP said he was making a general point about teaching qualifications.
The Labour politician’s comments prompted a storm on Twitter, with a number of Conservative MPs accusing him of “sneering”.
But responding himself on Twitter, Mr Hunt wrote: “On BBC QT I was trying to make a generalised point about the use of unqualified teachers in schools.
“I obviously meant no offence to nuns.”
Mr Hunt clashed with Ms Odone during Thursday’s edition of the BBC One discussion show, in which education secretary Nicky Morgan was also a panellist.
Ms Odone, a former editor of the Catholic Herald, said: “The most inspiring teachers I’ve ever encountered were not out of teacher training college. You know what, they taught values, not British values, they taught real values.”
Mr Hunt interrupted, saying: “These were nuns. These were all nuns, weren’t they?”
He added: “I know about your religious schooling and there’s a difference I think between a state education system having qualified teachers in the classroom.”
Labour would make it compulsory for all teachers in state-funded schools to be qualified – and would reverse the coalition government’s decision to allow free schools and academies to recruit unqualified teachers.
Writing afterwards about the exchanges, Ms Odone questioned “why is it acceptable to denigrate anything Catholic but bleat tolerance about every other religion?
“To know he and Labour stand a chance at the next election makes me fear for the 7,000 brilliant faith schools in this country,” she told the Catholic Herald.
Gordon Brown’s former spin doctor Damian McBride, who has worked for Catholic charity Cafod, tweeted: “Oh Hunty. My mum spent most of her career teaching in a ‘convent school’, working alongside nuns. They gave incredible educations.”
Conservative MP Conor Burns, writing on Twitter, said: “Absolutely shocking, sneering comments by Tristram Hunt about Catholic schools and nuns. I was educated by Brothers. Gave lives of service.”
Fellow Tory backbencher Nadine Dorries accused Mr Hunt of “sneering down his nose” at Ms Odone “because she is a Catholic”, adding that he was “bang out of order”.
She later added: “If Labour had any chance of holding onto its Catholic Glasgow seats, it lost it last night with Tristram Hunt’s remarks.”
Ruth Davidson, the Conservative leader in Scotland, said the Labour frontbencher had made a “gross misjudgement”.
But Hugo Rikfind, a columnist for The Times, said Mr Hunt’s comments had been misinterpreted and what he had meant by “but they were nuns” was “that’s hardly untrained”.