Tekashi69 Claims UK Immigration Lied to Keep Him Out of the Country

Tekashi69 believes UK customs agents refused him entry into the country because of his recent rap beefs ... and concocted lies about his criminal past just to keep him out.

6ix9ine was set to play 2 sold-out shows this week -- one in London, and another in Manchester. We're told the rapper was held at immigration Thursday for 12 hours after arriving from Belgium.

Sources close to 6ix9ine tell us customs agents repeatedly told the rapper they flagged him because he spent more than 12 months behind bars ... a buzz kill for foreigners who want to enter the country. Our sources say, not only has Tekashi never spent anywhere near 12 months behind bars, his team worked months in advance to insure he had all the proper paperwork and sponsors for entry.

Not only were the UK shows sold out, we're told they were also big time business opportunities for Tekashi as he planned on livestreaming them for fans on Xstreampass.

Our sources say Tekashi and crew feel the real reason they were refused entry is because of Tekashi's recent antics, including his feud with Chief Keef, and they've made stuff up to illegally bar him.