Kemi Badenoch has said she would reverse Labour's "cruel family farms tax" as farmers warned the plan would "decimate the countryside".
The new Conservative leader used her first Prime Minister's Questions to ask Sir Keir Starmer how he will help farmers facing uncertainty after last week's budget.
Chancellor Rachel Reeves announced last Wednesday 20% inheritance tax - a 50% reduction from normal inheritance tax - would apply to farms worth more than £1m from April 2026, where they had previously been exempt.
Politics latest: Starmer fights fire with fire at PMQs
The announcement has caused a row as farming unions and Opposition critics have argued it would make the UK more reliant on imports and food prices would rise as they would have to sell off land to pay the tax.
Some have accused the government of failing to understand how farming works as most farms are asset rich yet cash poor.
Ms Badenoch said her party would reverse the plan and asked the government to "reassure" farmers who are worried about the move.
She told the House of Commons: "I am very clear that we would reverse Labour's cruel family farms tax."
The Tory leader added: "We have heard him repeat the lines on the television, fixing the foundations and so on.
"What can he say now to reassure the farming community who provide security for the whole nation?"
Sir Keir responded: "I'm glad she's raised farmers. Because the budget last week put £5bn over the next two years into farming.
"That's the single biggest increase, unlike the £300m which was underspent under the last government.
"But when it comes to inheritance, the vast vast majority of farmers will be unaffected, as she well knows; as they well know."
Read more:
'A dark day': MPs react to Donald Trump's victory
Who is in Kemi Badenoch's shadow cabinet
Earlier in the day, Wales Secretary Jo Stevens told the Commons couples can pass farms worth up to £3m to their children tax free due to other tax reliefs.
However, that has not quelled feelings, as about 50 farmers protested outside the Northern Farming Conference in Hexham, Northumberland, on Wednesday, where farming minister Daniel Zeichner was due to speak.
One farmer said he was worried about "getting to the next harvest" due to cuts to delinked payments, while another said his inheritance tax bill would be pushed "to an almighty level" with "massive repercussions for the next generation".
Iain Brown, 50, whose farm is in north Northumberland, told PA his message to ministers is: "Don't be frightened to row back because you're going to have to, or you are going to decimate the countryside.
"It will change beyond belief and it will be going to big companies who won't care."