CONTRARY to the comments attributed to Jim Murphy and Stewart Hosie in your front-page news story ("Conservatives accused of 'betraying Scotland' on tax", The Herald, April 15) , there is nothing in the Conservative Party manifesto contrary to the Smith Commission Agreement and there is nothing in it that will bar Scottish MPs from voting on the Budget.

The Smith Commission Agreement states that "income tax will remain a shared tax". Under the agreement it will be for the Scottish Parliament to set the rates and bands of income tax for Scottish taxpayers' earned income, but it will continue to be for Westminster (1) to define income for the purposes of the Taxes Acts; (2) to set the personal allowance (that is, the point at which earnings become taxable as income); (3) to define "Scottish taxpayer"; and (4) to control income tax as it applies to savings.

MPs representing seats across the whole of the UK (including Scotland) will continue to decide all four of these matters. But, as the setting of rates and bands for Scottish taxpayers will be for Holyrood, so it must follow that the setting of rates and bands of income tax for taxpayers in the rest of the UK must be for MPs representing the rest of the UK: such is only fair. All of this is perfectly compatible with what the Smith Commission Agreement said about income tax.

Prof Adam Tomkins FRSE,

Member of the Smith Commission and Professor of Public Law at the University of Glasgow,

School of Law, Stair Building, 5-9 The Square, University of Glasgow, Glasgow.