Two senior members of the Cabinet have become embroiled in a bitter row over allegations of extremism in state schools in Birmingham.
Home Secretary Theresa May has accused Education Secretary Michael Gove of failing to deal with an alleged Islamist plot to take over schools.
It is understood Mr Gove believes Mrs May's department does not react strongly enough to extremism.
But a spokesman said they were working "energetically" together on the issue.
'Someone else's problem'
In a letter, Mrs May said: "The allegations relating to schools in Birmingham raise serious questions about the quality of school governance and oversight arrangements."
She added: "Is it true that Birmingham City Council was warned about these allegations in 2008? Is it true that the Department for Education was warned in 2010? If so, why did nobody act?"
Mr Gove believes there has been a plot by extremist Muslims to take over schools in Birmingham, according to The Times.
He thinks there is reluctance to tackle the issue in government departments, especially Home Office.
But a Home Office source told the BBC "he was trying to make it someone else's problem".
Those around Mr Gove pointed out it was his view that for over a generation there had been a reluctance in Whitehall to confront extremism unless it developed into terrorism - and his criticism did not relate specifically to the current home secretary.
But a Home Office source was blunt, telling the BBC: "The Department for Education is responsible for schools, the Home Office is not."
"They have got a problem and they are trying to make it someone else's problem," the source added.
A source close to Mr Gove said the education secretary thought "Theresa May was an excellent home secretary".
The BBC's political editor, Nick Robinson, said the row amounted to "an old-fashioned Whitehall turf war", with two senior ministers differing over how to combat Islamic extremism.
"I understand that Michael Gove and Theresa May clashed at a recent meeting of what's called the Extremism Task Force - a committee of cabinet ministers set up by David Cameron.
"They argued about how to define extremism. Mr Gove has long argued that Whitehall is too soft on extremism; that it only confronts people once they've turned to violence; that you should 'drain the swamp' and not wait for 'the crocodiles to reach the boat'.
"At the meeting he argued for a broader definition. Mrs May, for a narrower one. She won."
Nevertheless, the pair have insisted they are united.
In a statement, they said: "The Department for Education and the Home Office take the problems in Birmingham schools and all issues relating to extremism very seriously.
"Michael Gove and Theresa May are working together to ensure we get to the bottom of what has happened in Birmingham and take the necessary steps to fix it."
A government spokesman added: "There is no difference between the education secretary and the home secretary who are both working energetically together to tackle the challenge posed by any form of extremism."
But Tristram Hunt, Labour's Shadow Education Secretary, said now was not the time for a Whitehall turf war.
"Michael Gove has failed to act on the early warning signs to prevent the sort of situation we are seeing in schools in Birmingham.
"But by refusing to act, Michael Gove is paving the way for more fragile schools to run into trouble."
Shadow Home Secretary Yvette Cooper said: "For two such senior ministers to launch a vitriolic public blame game in this way is appalling and irresponsible when they should be working together to sort out such serious problems.
"Preventing extremism is immensely important - in communities and in schools. The truth is that Michael Gove's reforms have made it easier, not harder, for schools to be run inappropriately.
"This is bad government and David Cameron should sort it out."
Three of the Birmingham schools inspected in the wake of the so-called Trojan Horse allegations have published the findings of their Ofsted reports.
They are rated "outstanding" or "good", although one urges governors to prepare students for "multicultural Britain".
The inspection of 21 schools in Birmingham was a response to claims of a takeover strategy by a hardline Muslim group.
Although there have been plans for all the inspection findings to be published together, this has been pre-empted by repeated reports that five or more of the schools have been found inadequate.
Individual schools, with positive outcomes, have also begun to publish their own report findings.
These include Ninestiles School - an academy in Acocks Green - Small Heath School, and Washwood Heath Academy.
A spokeswoman for the Department for Education spokeswoman said it investigating all evidence put to it in conjunction with Ofsted, Birmingham City Council and the police.