The Chancellor will have no power to solely remove the head of the independent Office for Budget Responsibility (OBR), George Osborne has pledged.
The provision will be included in the Finance Bill, which is currently undergoing its third reading in the House of Commons.
Only under "exceptional circumstances" would the Chancellor be able to unseat an OBR chairman, Osborne said in a letter to Committee chairman Andrew Tyrie MP.
Previously in his evidence to the Committee on the Budget, the Chancellor gave the group of MPs ultimate veto on the appointment of the chair of the OBR.
But in his letter he said: "I also wish to ensure that the chair cannot be removed at the whim of the Chancellor.
"The Bill will contain provisions to the effect that the chair may be removed by the Chancellor only under exceptional circumstances and with the express agreement of the TSC [Treasury Select Committee]."
The Committee yesterday published its report on the June 2010 Budget, in time for the third reading of the Finance Bill in the House of Commons.
In evidence to the Committee, the chair of the interim OBR Sir Alan Budd supported Osborne's latest proposal, saying neither the Chancellor nor the Committee should have sole power to dismiss the head of the OBR.
The Treasury Committee will take further evidence on the issue on Thursday and is expected to report on it by the autumn.
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