Ex-Germany captain Philipp Lahm has confirmed he is taking legal advice over a spoof April Fool's story gone wrong.

A Munich-based fitness start-up issued a grovelling apology to the World Cup winner over a fake April 1 story, which hit the German media last Saturday, falsely claiming he had invested in them.

The story even contained a fake quote attributed to the Bayern Munich star after an employee decided to circulate an internal newsletter to the German media without the knowledge of the company's bosses.

"It was an April Fool's joke which should have been sent exclusively to our members in a newsletter," explained the company's red-faced co-founder.

However, the stunt quickly backfired and although the firm apologised several times, Lahm failed to see the funny side with the prank having generated plenty of free publicity for the start-up.

"I'm taking advice and bringing the matter to the detailed attention of a lawyer," said the 33-year-old.