Ministers insist “three quarters of estates will continue to pay no inheritance tax at all, while the remaining quarter will pay half the inheritance tax that most people pay, and payments can be spread over 10 years, interest-free”.
One farming union warned last month that Welsh family farms have been thrown into “turmoil” by the changes.
Speaking at the Royal Welsh Show in Llanelwedd, Mr McLean, firmly backed the farmers in the argument.
M&S, he said, was “very, very clear” that agriculture should be treated differently by the government.
“The whole taxation system was devised to recognise that the margins of profitability in agriculture weren’t like other industries,” he said.
“That’s why you had a difference in how the inheritance tax approach was set up.”