Sashi Dhar Sahnan is thought to have been involved in a £1.5m deal to ship the class A drug into the country, hiding the stash in air conditioning units.

The 51-year-old is being sought by Leicestershire Constabulary, who believe he has connections in Northampton and could have fled to the county. The force has now urgently appealed for information from anyone who may know where he is.

Det Insp David Sandall, who is leading the investigation, said: "We urgently need to trace Sahnan. We know he has family in the Birmingham area and has associates in London, Belfast and Northamptonshire."

He added: "Sahnan wears a hearing aid in his right ear. We are asking people to look very closely at this picture; do you recognise the face? Have you seen him in your area?

"If you know where he is, please do not approach him; call us immediately. We can assure you any information will be treated with the utmost confidence and if people are fearful of giving their names, they can contact Crimestoppers anonymously."

The huge quantity of heroin was discovered and seized by HM Revenue & Customs and police in a joint operation in July last year. Customs officers found the drugs hidden in pallets upon which the air conditioners were being transported.

Three women and 15 men from Leicester and Birmingham were arrested as a result.

Steve Roper, detection manager for the UK Border Agency, said: "This was a highly organised and sophisticated smuggling plot to bring a large quantity of class A drugs into the UK."

Anyone with information can call Leicestershire Constabulary on 0116 222 2222.