Sir Stephen Bubb, chief executive of Acevo, will ask Cabinet Office minister Francis Maude and civil society minister Nick Hurd to deny press reports that the job of Dame Suzi Leather, chair of the Charity Commission, is under threat.

Press reports in the Sunday Times this week claim ministers are keen to sack Dame Suzi Leather for her ‘politically motivated’ attacks on public schools.

Some ministers have reportedly looked at Leather’s contract, which was renewed in 2009 for a second three-year term, and found they can terminate it early.

The Times reports a government source saying: "She should be given some time to prove she can work constructively with us.

“But her appointment is in the gift of the Secretary of State. He can terminate it. We want to see a different approach at the Charity Commission and an end to the politically motivated statements."

Writing in his blog, Sir Stephen called the report "shocking", and suggested that some ministers were angered at her outspoken criticism of cuts to the sector:

“Suzi has the confidence of the sector. We applaud her for speaking about how cuts are damaging charities,” he said.

“That is her job. She is not a government stooge. The idea that the appointment of the chair of the Charity Commission should be dependent on the political whims of a government minister is disgraceful.

"I shall be seeing Francis Maude and Nick Hurd and shall ask for a denial.

“We need to beware.  As things start getting nastier we can expect more attacks from unnamed sources. The snide remarks about big charities are but a start. I'll be watching this one carefully.”