Lib Dems leader Ed Davey joins protestpublished at 14:39 Greenwich Mean Time
Leaders of opposition parties also joined farmers during their protest in Westminster.
Liberal Democrat leader Ed Davey earlier told farmers "you deserve so much better", the PA news agency reports.
He said that farmers are "fed up with being let down and taken for granted", and called the inheritance tax change "stupid".
Speculating that it will cause farms to sell up, he asked: "Who else will put healthy, nutritious food on our tables... If we lose the families who have been doing it so passionately for generations?"