Seafarers have told the BBC port officials routinely demand cash, cigarettes, food and drink as bribes before allowing ships through.

So-called “gratuities” are against international anti-corruption laws. But the Maritime Anti-Corruption Network said it received 5,183 reports in 2023.

The International Association of Ports and Harbours is working to tackle it.

Ex-captain Stephen Gudgeon said he was once held at gunpoint after refusing to hand over cigarettes at a port in Asia.

“They took me ashore at gunpoint and I was locked up. I was photographed and fingerprinted, and I was interviewed by two officials in an empty room with just a chair, which I was locked into,” he told the BBC.

“And it was when they said to me, ‘Would you like us to inform your family of your detention?’ that I really got quite worried.”

Mr Gudgeon said eventually he was released with a $1,500 (£1,200) fine to pay for paperwork irregularities, which he believed were spurious and in retaliation for not handing over the cigarettes. The BBC has been unable to reach the ports authority in question to ask about the allegations.

The MACN told the BBC it had received 61,000 reports in more than 1,000 ports across 150 countries since it opened an anonymous helpline in 2011.

Cecilia Muller Torbrand, the head of the MACN, said experiences as intimidating as Mr Gudgeon’s were uncommon but that the shipping industry was “quite exposed to corruption risks”, and that the number of incidents reported would be “the tip of the iceberg”.

She said this was due to “the combination of frequent government interaction, shipping across multiple jurisdictions and the time element of sailing in and out of ports”.