Gary Coomber blames the organophosphate dips, which come from the same chemical family as nerve gases, for years of ill health, including a cardiac arrest.
The move comes amid growing controversy over OPs, which have been blamed for a wide range of health problems, from multiple sclerosis to depression.
It is seen as having important implications for others who claim to have suffered as a result of exposure to organophosphates. An estimated 500 people have blamed ill health on such exposure.
Mr Coomber's lawyers, Leigh, Day and Co, confirmed that legal aid had been granted. It is not known when the writs will be served.
"We are delighted that we have been granted legal aid and I expect the writs to be issued shortly," Mr Coomber said.
He was exposed to OP dips on his farm in Kent between 1988 and 1991. He says his health suffered seriously; he was admitted to hospital and he had to be resuscitated after his heart failed. He still suffers some health problems as a result, he says, of that exposure.
Meanwhile, a psychiatrist treating more than 20 farmers has urged the withdrawal of OP dips.
Dr Bob Davies, consultant psychiatrist for the Avalon NHS Trust, has written to the Chief Medical Officer about his patients, and says that if the OPs were a pharmaceutical drug, they would have been withdrawn.
He said: "All the OP-exposed farmers that I have interviewed have been on the verge of killing themselves, and then for various reasons have drawn back from the brink."
He says in his letter that the degree of suicidal thinking is dramatically higher compared to other psychiatric patients.
Mr Davies goes on: "I am sure that if this were a pharmaceutical agent, such a weight of evidence would result in its withdrawal from the market. I find it difficult to understand why the same criteria are not applied to environmental toxins."
He said yesterday: "The Government's position is that there is no proof. I have to dispute that. There are a number of reasons to suppose that OPs are directly associated with disorders of mood."Reuse content