Delhi international airport is being sued after it awarded a lucrative duty-free contract to a consortium that involves Aer Rianta.

Flemingo, an Indian company that unsuccessfully bid to manage duty-free operations at a new terminal at Delhi, claims a "lack of transparency" in the bidding process by the airport operator to a group that involves Delhi airport, Aer Rianta and a local group called Indian Duty Free Services.

In court documents, Flemingo accuses the airport of "discriminatory, arbitrary, illegal and violative" action of its "fundamental rights".

It also hit out at the $50m cash security deposit required of all bidders, the Moodie Report, a travel and retail industry newswire, reported.

Delhi's new terminal three, when it opens next year at the officially-named Indira Gandhi International Airport, will be one of the largest in India, handling 34 million passengers a year. The winning consortium involves Aer Rianta and the local group, who between them control 50.1% of the duty-free operating company, and Delhi international airport, with the balance of 49.9%.

Flemingo is also suing over the awards of duty-free contracts at Mumbai and other Indian airports.

The award to the Aer Rianta group in June to manage the 4,000 sq m outlet was the first time that Aer Rianta had won a foothold in India. An offshoot of the Dublin Airport Authority, the Shannon-based duty-free company operates airport retail operations in North America, Russia and Bahrain.

A spokesman for the Dublin Airport Authority said it could not comment on the case. Delhi airport said Flemingo had a track record of suing other airports.