The boss of the firm which owns British Airways has said a British exit from the European Union would not have a "material impact" on the business.

But Willie Walsh, chief executive of International Airlines Group (IAG) which also includes Ireland's Aer Lingus and Spain's Iberia, said the possibility of a so-called Brexit was causing uncertainty in the market.

He made the comments as IAG announced an operating profit before exceptional items of 2.3 billion euros (£1.8 billion) in 2015, an increase of 68% on the previous year's figure.

Asked what impact a Brexit vote would have, Mr Walsh told the BBC Radio 4 Today programme: "We have taken advice from a number of sources, we have looked at this internally, we have undertaken a risk analysis.

"Obviously there is uncertainty in the market which is weighing on people's minds. But our view is should there be a vote we don't believe it will have a material impact on our business."

Earlier this week, Michael O'Leary, boss of rival airline Ryanair, said he would actively campaign to keep the UK in the EU.

Mr O'Leary accepted that Brexit would not be "the end of the world" and predicted that it alone would not cause UK air fares to rise.

But he warned there would be "undoubtedly three or four years of uncertainty and less economic growth".

IAG's increase in profits was partly driven by tumbling oil prices, which have fallen some 70% since the summer of 2014 due to oversupply and falling demand from emerging nations such as China.

Mr Walsh said IAG typically buys its fuel three years in advance so he predicted "some further benefit" for the company next year.

He described the firm's results as "very strong" and claimed they reflect the "strong performance" of all the airlines within the group.