Labour shadow Home Secretary Yvette Cooper has accused Theresa May of breaking the ministerial code, and called on her to explain her conduct.
Speaking to ITV News Political Correspondent Libby Wiener, she said
"We still have silence from the Home Secretary, even though the Education Secretary has apologised, and it does seem that she too has broken the ministerial code."
The leaking, from her department, of a letter to Michael Gove, raises serious questions for the Home Secretary to answer.
One school was praised by Ofsted for using money from the pupil premium to pay for a number of cultural trips to Saudi Arabia.
Six Birmingham schools will be rated 'inadequate' and several more downgraded. Council officials have been criticised for failing to act.