Politicians from Angela Merkel's conservative Christian Democratic Union (CDU) and her former coalition partners, the business-friendly Free Democratic Party (FDP), have been accused of taking bribes in the form of party donations from Germany's most notorious gunmaker, Heckler & Koch.

An investigation published Tuesday by the regional public broadcaster SWR and the taz newspaper uncovered emails and an internal H&K report which showed that the company in 2010 tried to bribe Bundestag members from the two parties to make sure that the government approved the sale of guns to Mexico. Increasing corruption within the security forces in Mexico and an ongoing war with drug cartels had by then caused the German government to get cold feet about selling weapons to the country.

Six former H&K employees, including ex-CEO Peter Beyerle, are on trial in Stuttgart at the moment over what prosecutors say was the illegal export of several thousand G36 assault rifles to Mexico from 2006 to 2009. According to taz, Beyerle wrote emails to colleagues in March 2010 saying that since it was becoming harder to sell guns to Mexico, it would be worth exploring the "political route." He then asked the firm's advisory council to make donations to the CDU and the FDP.

Read more: How a German gunmaker became one of the world's deadliest

Business-friendly parties

The reports say that the local branch of the CDU in Rottweil-Tuttlingen, Baden-Württemberg, received €10,000 ($11,790) from H&K — just below the official declaration threshold. As well as being the CDU branch closest to H&K's headquarters in Oberndorf, Rottweil-Tuttlingen is the constituency of Volker Kauder, head of the CDU's parliamentary group and one of the most powerful people in Merkel's party.

The trial against Beyerle and other former H&K colleagues began last week

Similarly, the local party branches of two important FDP politicians, Ernst Burgbacher and Elke Hoff, received €5,000 each from the gun manufacturer, which arms several NATO militaries. Burgbacher was then parliamentary deputy secretary in the German Economy Ministry, which approves foreign exports, while Hoff was FDP defense policy spokeswoman and considered influential in the defense industry. The reports said that Beyerle asked Burgbacher in writing to help with future Mexico deals.

SWR also revealed that Stuttgart state prosecutors had already been aware of the donations, and had opened and then closed a corruption investigation into Beyerle back in January 2017 — on the grounds that any eventual punishment would not be significant compared to the punishment Beyerle is threatened with in the illegal arms deal trial.

H&K did not want to comment on the fresh allegations on Wednesday other than to say, in an email to DW, "We have been cooperating with the investigative authorities from the beginning. This is in our interests." The ongoing public scrutiny appears to have had an effect on the company strategy, which has sincestopped all deals with non-NATO and non-EU countries. H&K has now begun to concentrate on the US domestic market.

Read more: How German firms donate secret money to political parties

Conspiracy suspicions

The peace activist Jürgen Grässlin, who brought the charges against the H&K employees over the illegal Mexico deal, has long expressed suspicions that Beyerle — a retired judge in Baden-Württemberg — is being sheltered from more serious consequences by a friendly state judicial system. It took eight years for prosecutors and local courts to bring the case to trial. Nevertheless, the presiding judge at the first day of proceedings last week specifically dismissed the allegation, arguing that more important cases had to be dealt with first.

Kauder is considered one of the most powerful politicians in Merkel's CDU

"Clearly H&K wanted to use party donations to FDP and CDU Bundestag representatives to get the then-government parties in Berlin to approve further exports of G36 assault rifles to Mexico," Grässlin said in a statement. "This form of corruption would have brought more death, because H&K weapons have been used to kill and murder in Mexico for years."

For Grässlin, the emails represent the first concrete evidence of his long-held suspicion — that the German government actively helped H&K to circumvent its own export controls.

"The role of Volker Kauder will be central to the investigation," Grässlin added. "Kauder's role as lobbyist for Heckler & Koch became more than obvious when the H&K majority shareholder Andreas Heeschen thanked him personally for his support for arms export deals at a press conference in 2009."

This was telling, Grässlin argued, because Kauder has never worked for the Economy Ministry and doesn't sit on the National Security Council, the two bodies that approve Germany's arms deals. "But Kauder is just the right-hand man for Chancellor Angela Merkel, who as chairwoman of the National Security Council supported and supports these exports," he said. "So the trail goes all the way to the top."

The new revelations also pose general questions about Germany's opaque party donations system, which allows companies and individuals to donate up to €10,000 without having to declare it. Germany does not have a lobby register that makes all lobbying activity public, a controlling measure that is standard among other democratic countries. Lobbying campaigners have long argued that this leaves the German government especially vulnerable to bribery.

The CDU and the FDP both remain opposed to a lobby register, and neither responded to a DW request for comment on the new allegations.