Boris Johnson appeared to joke about sex tourism in Thailand during a major speech about Brexit.

In an address in which Foreign Secretary outlined his vision for the country’s departure from the EU, he also quipped “the right deal on aviation and on visa-free travel” would allow Britons “ever more intensively to go on cheapo flights to stag parties in ancient cities”.

Mr Johnson said: ”As I have just discovered we have more than a million who go to Thailand every year, where according to our superb consular services they get up to the most eye-popping things.

“If we get the right deal on aviation and on visa-free travel – both of which are in our mutual interest – this expansion of UK tourism will continue, not just beyond the EU, but within the EU itself; and we will continue ever more intensively to go on cheapo flights to stag parties in ancient cities, meet interesting people, fall in love, struggle amiably to learn the European languages whose decline has been a paradoxical feature of EU membership.”

The Foreign Secretary’s comments, made in a ‘Road to Brexit’ speech in which he attempted to reach out to Remain supporters, were described as “off-colour” and  “embarrassing” by some on social media.

One Twitter user said: “Boris Johnson going on about Brits committing illegal activities in Thailand and stag parties in ancient cities. This is our international reputation? How sad.”

Another wrote: “Harming our reputation and making light of serious behaviour, even criminal abuse, is a step too far even for him.”

Mr Johnson met Thailand’s Prime Minister and Foreign Minister during a tour of Asia this week.

After talks on trade and security, he said he would “look forward to further strengthening the UK’s relationship with Thailand in the future”.

The Independent has contacted the UK Foreign Office for a comment.