International Airlines Group boss Willie Walsh has offered Sir Richard Branson a “knee in the groin” according to reports.

The outspoken chief executive was responding to the offer of a £1 million bet from Branson that his Virgin Atlantic airline would still be around in five years.

According to reports in the Guardian, Walsh said he did not have £1 million, so wagered something “as painful to him as it might be to me” instead.

“I don’t have £1m, so a knee in the groin, maybe - that would be as painful to him as it might be to me,” Walsh is reported to have said.

As part of a wider attack on Branson, Walsh also said he doubted the Virgin chief’s influence on the airline industry.

“I just don’t see that the guy has anything that stands out in terms of what he has achieved in the industry,” Walsh said, as reported by the Telegraph.

“I’ve said it publicly, I don’t respect him in the way I respect other people in the industry, and that’s a personal view.”

Branson offered the £1 million bet that Virgin would still be around in five years after Walsh suggested the brand could soon disappear.

This followed reports suggesting Sir Richard may sell some of his 51 per cent stake.