Two big UK tobacco companies have failed to persuade the high court to strike out a case against them that alleges they are responsible for the exploitation of Malawian farming families and child labour in their drive for profits.

British American Tobacco and Imperial Tobacco deny the allegations. They argued that the Malawian families could not prove that the tobacco they grew had ended up in their cigarettes.

The farmers’ lawyers said they had repeatedly asked the companies for proof that they had not bought tobacco from their clients, but no documents had been disclosed to them.