Ryanair executives will face questioning by Belgian investigators as part of an inquiry into a local marketing company jointly owned by the Irish airline and Charleroi airport, the head of the airport said.

Ryanair chief operating officer Michael Cawley and Bernard Berger, head of flights development, have been called to meet with investigators next month, according to Laurent Jossart, the managing director of Charleroi airport.

The investigation centres on a Belgian company called Promocy, which finances the advertising of Ryanair's routes and fares to and from Charleroi airport, according to Mr Jossart. Charleroi public prosecutor Nabil Sanaji said that the examining magistrate was looking into suspected fraud and misuse of funds allocated to Promocy.

Mr Jossart and another Promocy board member were questioned in May and were asked by investigators to invite Mr Cawley and Mr Berger for questioning in Belgium in December.

A spokeswoman for Ryanair declined to comment on the investigation last night.

"From the airport side, we are quite optimistic because we believe we were complying with guidelines issued a few weeks ago by Europe and because our accounting was done by Deloitte," Mr Jossart said. "We have asked that the investigation is speeded up because when you have an investigation, the popular thinking is that you are guilty."

Ryanair announced that it will halve the number of its flights to the resort of Newquay after Cornwall County Council imposed a £5 (€7.29) surcharge on the airline's passengers.

The carrier will withdraw 12 flights a week to Newquay, leading to a loss of 100,000 passengers a year to the town's airport.

The county council introduced the surcharge a month ago. - (additional reporting by Reuters)