An HTA submission to the committee says imports are good because they bring "international aid to help countries in Africa develop their industries to increase living standards, and preferential access for cut flowers from certain South American countries, purportedly to try to tackle trade in drugs".
It adds that plant imports are not always to blame for diseases entering the UK. While ash dieback and oak processionary moth came in on imported trees, Asian longhorn beetles have been associated with imports of stone in wooden packaging from South-East Asia while Dutch elm disease entered in railway sleepers.
The statement concludes with the HTA demanding "no tax on gardening".
In evidence provided on behalf of the HTA, Binsted Nursery director Martin Emmett said of the 75,000 garden plant entries in the RHS Plant Finder, most are non-native. "The European trade in horticulture is very competitive already and any such levy would simply reduce the competitiveness of the UK industry," he added.
He warned of polarisation between conservationists and horticulturists on the issues after MPs Zac Goldsmith and Alan Whitehead questioned him on levies and banning imports.
The committee heard from conservation groups before hearing from Emmett, who attacked the international plant trade as a pest and disease spreader.
Emmett advocated "a fully integrated landscape approach (that) would encompass, but not be limited to, interests as diverse as food production, conservation, forestry, housing, gardening, urban greening, land use for renewable energy and tourism".
He added: "With respect to landscape management, there is a tendency for politicians to respond primarily to the arguments from wildlife conservation organisations and we see this happening in the inquiry into invasive non-native species.
"The conservationists' concerns are relevant but so are the concerns of the garden sector, which plays such an important role in making our populated environments pleasant to live in."