Germany captain Philipp Lahm has branded the mole who has been leaking team line-ups to the media as a "disgrace" and admits the spy could be damaging their chances of winning the Euro 2012 title.

Germany will play their Euro 2012 semi-final in Warsaw on Thursday with Joachim Loew's team aiming to lift their fourth European crown but first since 1996.

The Germans have been rattled by a mole who is leaking team line-ups to their media ahead of their Euro 2012 matches.

Loew sprang a triple surprise for Friday's quarter-final by dropping Mario Gomez, Lukas Podolski and Thomas Mueller for the 4-2 quarter-final win over Greece in Gdansk, but the changes had already been reported earlier that afternoon.

"It is a great pity if leaks like this occur and it is a disgrace that the line-up was in the public domain so early," said Lahm.

"The whole nation is standing behind us, everyone wants to move ahead and lift the trophy.

"The person who has the problem is the guy responsible for leaking that information, because at the end of the day, he might be damaging the hopes of a nation.

"Maybe that person hasn't understood how team team sports work. I think it is a shame, but we won't be hiring any detectives."

Loew has already addressed the squad about the issue and has said: "It is not good when the cards are on the table so early".

Now Lahm insists the Germans have to be more careful about who they pass team information too.

"This is an issue for us, everyone has to be aware about who he gives information about team selection to," said the 28-year-old.

"We have to be extra careful from now on.

"It is normal for players to tell their wives or girlfriends if they are playing or not, but it is out of the question to pass the complete line-up onto an agent.

"We can share information with the closest family, but that is about it."

It was common knowledge ahead of the opening Group B match against Portugal that Loew intended to play Gomez, rather than Miroslav Klose, up front and he dropped Arsenal defender Per Mertesacker for Borussia Dortmund's Mats Hummels.

News also leaked prior to the final group game against Denmark that Bayer Leverkusen midfielder Lars Bender would be used at right-back for the suspended Jerome Boateng.