Curtis-Machin said the allowance was justified after Parliament voted down changes this month because "we are a unique sector dealing with live product".
He said the HTA had not given up on extensions after years of failure: "We’ve got to keep going with it."
Suggestions are that the Enterprise Bill, which had an amendment to allow extensions, was badly drafted and that allowed SNP to vote to defeat it, rather than bringing the bill under English Votes for English Laws.
Scotland has already extended trading on Sundays. Curtis-Machin said he did not know if this was the case but added that Osborne was "fed up with the SNP’s small-minded behaviour" and that the exemption for garden centres could "redress the balance".