A strictly Orthodox school has come under renewed attack from secular campaigners for reportedly stopping girls from answering exam questions.

The National Secular Society (NSS) has written to Ofsted and the Department for Education, calling for an inquiry into the state-aided Yesodey Hatorah Girls High School in Hackney, North London.

The NSS complained about the school last year when it emerged that Yesodey Hatorah had covered up a question in a GCSE science paper which it regarded as unsuitable.

Initially, the practice was allowed by the exam board as long as parents approved, but was banned this year by exam regulators.

Now the NSS has acted again following a claim by a local newspaper last month that pupils at the school were being discouraged from answering exam questions.

In a letter to Ofsted, NSS campaigns manager Stephen Evans said: "We are concerned that this school, and potentially other schools with a religious character, may be failing to teach the national curriculum in full when scientific facts clash with its ethos."

Yesodey Hatorah principal Rabbi Avraham Pinter explained that it would avoid teaching certain topics because of its religious principles.

But he added: "If pupils were asked a question about The X Factor, for example, they would know not to answer it. They wouldn't need to be told on the day not to answer it."

Yesodey Hatorah was rated a good school after a recent visit by Ofsted inspectors, who noted that girls achieved above-average GCSE grades.

The DfE is looking into the NSS allegations. "We expect every school to be acting in the best interests of its pupils," a spokesman said. "If a school is encouraging pupils not to answer exam questions, it is clearly limiting what young people could achieve."