MDPE fitted to garden tap - help

[ashesofroses]

I am trying to fit MDPE 20mm pipe to a threaded garden tap for the water source for garden irrigation, it always leaks from the MDPE fitting - i have tried various adaptors, what am i doing wrong? thank you

 

[WC1]

https://www.NoLinkingToThis/p/floplast-female-pipe-adaptor-20mm-x/32438

Should secrew on to the bib tap. You need an insert for the mdpe.