Former Wickes boss Bill Grimsey is advising Labour on business strategy and working as an ambassador to the high street for the party, in a bid to promote the opposition among firms and to feed information back into its policymaking teams.
He has proposed the party levy a new tax on business premises, and to redistribute some of the funds raised to poorer areas in a bid to revitalise more run-down high streets.
Grimsey also called for farms to become subject to rates, ending the historic exemption for the sector.
But Labour rejects any tax rises on small firms and denied the advisor speaks on behalf of the party.
“This is not a Labour party report or a Labour party policy,” said a spokesperson. “A future Labour government would cut business rates for small businesses.”
Sources at the party said Grimsey had made the proposals for new taxes before he became an advisor.