Using Ofsted to force schools to set their pupils by ability was branded “bizarre” by one of the watchdog’s national directors.

The criticism came as another national director suggested teachers should act as whistleblowers and inform Ofsted if they have concerns about their school.

Sean Harford, an HMI and Ofsted’s regional director for the east of England, condemned the notion of compelling all schools to set by ability that emerged this week.

Earlier this week, education secretary Nicky Morgan was forced to deny rumours that the Conservatives were considering bringing in plans to ensure every school sets their pupils by ability and to use Ofsted to police it.

Speaking at the ResearchEd conference in London, Mr Harford said: “The idea that we would go round schools and say if you set [your pupils] you’re outstanding, but if you don’t you require improvement is just bizarre and goes against everything we want to do.”

Mr Harford’s comments came before Michael Cladingbowl, Ofsted’s national director of inspection reform, told an audience of teachers that they should have no fear of telling Ofsted if they are worried about how their school is being run.

It comes just days after MPs were told that teachers in the schools at the centre of the Trojan Horse scandal were too afraid of approaching Ofsted for fear of it triggering a fresh inspection.

But while Mr Cladingbowl acknowledged that while teachers may be anxious of inspections it should not prevent them coming to the inspectorate with their concerns.

“I know people need to have confidence that they are going to get a fair deal [from Ofsted], but it’s about us building that confidence and building that trust [to come and approach us],” he said.

“It’s really important if a teacher is concerned about the way things are done, the practice or any aspect of their school, they should get in touch. Please, please do that. Because, like you, we don’t want things to go wrong in individual schools and often we don’t hear about things until it’s too late.”