For investors, the potential merger of Bayer and Monsanto provides a lucrative chance to own shares in an unassailable giant of the agriculture industry.

But this tie-up between two of the world’s most successful companies is not without controversy, not least because of the infamous past of both firms.

Some experts fear it will create a monster whose global tendrils stretch into everything from health care to farming.

Threat: With both Monsanto and Bayer heavily focused on genetically modified crops, the new company could become a top target for activists challenging the spread of so-called Frankenstein foods

And with both firms heavily focused on genetically modified crops, the new company could become a top target for activists challenging the spread of so-called Frankenstein foods.

Bayer’s £43billion offer for American rival Monsanto would form the largest agricultural giant the world has ever seen. It is the biggest takeover bid by a German business in history.

Bosses at Bayer have described the move as ‘an extraordinary opportunity’ – but there are reports of unrest even among its own shareholders, with one branding the move ‘arrogant empire-building’.

Monsanto – which is halfway through axing 3,600 jobs after a failed takeover attempt of its own last year – is expected to give a ‘positive answer’, according to Bayer boss Werner Baumann.

BAYER VS MONSANTO Bayer was founded in Barmen, Germany in 1863 by two friends who made dyes from coal.

In 1897 it developed Aspirin, the world’s first mass-selling drug – 20bn tablets a year are now sold in the USA alone.

Two weeks later, it invented heroin as a cough remedy. It was on sale until 1913 as ‘non-addictive’ medication.

A sister firm IG Farben produced Zyklon B, the gas used by Nazis to murder an estimated 1m Holocaust victims.

Monsanto was founded in St Louis, Missouri in 1901 and initially made food additives such as saccharin.

In the 1960s it became the first company to mass produce light-emitting diodes (LEDs).

It was a key producer of toxic Agent Orange. 11.4m gallons were sprayed on forests during the Vietnam War.

In 1983 it introduced genes into plant cells and became one of the first firms to genetically modify food.

But regardless of what the deal means for investors, it will combine two companies with rocky histories.

Founded more than 150 years ago in Barmen, an industrial town in western Germany, Bayer made its name with Aspirin.

Its scientists developed the painkiller from chemicals in willow bark after realising ancient folk remedies involving the tree had a ring of truth to them.

The company lost its trademark in Britain due to post-First World War confiscations. But Aspirin is nonetheless one of the most important and widespread drugs ever produced, with 40,000 tonnes manufactured every year.

Unfortunately, Bayer’s other early triumph was just as popular. In 1897, two weeks after he synthesised Aspirin, Bayer scientist Felix Hoffmann produced a powerful version of the ancient poppy-based drug opium.

He called it heroin and the product was sold across the world as a cure for coughs.

The company finally stopped making it in 1913 – but by then the genie was out of the bottle and thousands were already addicted to what is now a Class A drug.

Bayer was then absorbed into chemicals conglomerate IG Farben, a giant German firm made infamous by its use of slave labour in the Nazi era.

And IG Farben was involved in producing the gas Zyklon B which was used to murder an estimated one million Jews in concentration camps.

Bayer was once part of German firm IG Farben, made infamous by its use of slave labour in the Nazi era and involved in producing Zyklon B gas which was used to murder an estimated 1m Jews in concentration camps

Bayer was split back out from the conglomerate after the war – although German chemist Fritz ter Meer, who helped plan a concentration camp used for human experiments, served as its chairman for several years in the 1950s. The company’s bosses have apologised for its role in the Holocaust.

But there was one more controversy to come when in the 1980s Bayer was producing a treatment for haemophilia.

It was implicated in a major scandal after thousands of patients contracted Aids from contaminated blood, and reached a settlement with victims in 1997.

This dark past would overshadow anything in most other companies’ histories.

But 115-year-old Monsanto also has a string of controversies to its name. It was a key government partner in the Manhattan Project to build the first atom bombs, running a laboratory used to extract polonium, which set off their chain reactions.

Monsanto went on to produce industrial chemicals known as PCBs, which were banned across the world after being revealed as a possible cause of cancer.

The company ran a PCB plant in South Wales with waste dumped in the disused Brofiscin Quarry. It agreed to help pay for cleaning the site in 2015, but did not accept responsibility for the pollution.

Poison: MonsaNto played a key role in the production of the toxic Agent Orange fertilisers used by the US armed forces in the Vietnam War

It was also a mass producer of DDT, an insecticide used to kill malarial mosquitos. This was banned in the US in 1972 when it was credited with seriously damaging the natural environment.

The company – after playing a key role in the production of the toxic Agent Orange fertilisers used by the US armed forces in the Vietnam War – is now focused on seed production.

It is at the centre of a worldwide campaign for genetically-modified foods, despite widespread fears about the unknown effect these supposed super-crops could have on our environment.

Given this less-than perfect past, it is no surprise that Monsanto’s name could face the axe.