Earlier in September there was controversy when the government confirmed rules preventing the building of more Catholic schools would be relaxed.
At the time a government source said Catholic schools were "more successful, more popular and more ethnically diverse than other types of state school".
Some complained that the government's plans, tied in with proposals for more grammar schools, would cause poorer children to be left behind.
In a new interview with Channel 4 news the PM, herself a Christian, made a fresh call for more faith schools.
"What we want to do as a government is... increase the number of faith schools," said Mrs May.
She was challenged on her plans, which the journalist told her were not in the Conservative Party's 2015 election manifesto.
"I and every Conservative member of parliament that was elected in 2015 stood on an election manifesto to increase the number of excellent school places for children.
"There are one and a quarter million children who are not in schools that are good or outstanding.
"We need to increase the number of good school places."
She stressed that any new faith schools will need to prove that they are "genuinely raising the quality of education in an area".
Labour leader Jeremy Corbyn said of the plans: "Isn't all this proof that the Conservative Party... addresses none of the actual crises facing our schools system - a real terms cut in school budgets, half a million pupils in super-size classes, a crisis in teacher recruitment and retention, a rising number of unqualified teachers in classrooms, vital teaching assistants losing their jobs?
"Isn't this the case of a Government heading backwards to a failed segregation for the few and second-class schooling for the many?
"Can't we do better than this?"