The Earl of Courtown introduced a bill to the House of Lords this week to amend the 1994 Act in connection with the sale of horticultural supplies.
The HTA is behind the move, which would extend Sunday opening hours at garden centres from six to eight on Sundays and also allow opening on Easter Sunday. It is believed that this is the first time a gardening trade association has made such a move, which could mean 10 per cent extra turnover for centres - equivalent to tens of millions of pounds.
The Earl of Courtown, a landscaping business owner, said: "We're trying to get more people into garden centres and enable them to buy what they want. Many garden centres are small, family-run businesses and the Lords will support them. Many Lords are in the All-Party Parliamentary Gardening & Horticulture Group, too, so they understand the issues."
HTA director general David Gwyther said: "It's our job to ensure 20 million British gardeners have the best-possible access to garden centres, particularly during the short season, and this bill fits hugely well with increased interest in gardening coming as a result of climate change and our environment.
"Easter Sunday is one of the most important days in the plant-selling season. There are only 12 Sundays in the season and the extra two hours will be hugely helpful there, too."
A second reading is likely after Easter before committee stages, a third Lords' reading and then readings in the Commons. The bill could become law in two to three years.