The group, one of Germany's biggest, is already embroiled in another corruption row that has rocked the country's business establishment.
Two weeks ago, chief executive Dieter Vogel was arrested at its Dusseldorf headquarters along with eight other top managers over an alleged fraud during privatisation of an East German metals firm. All were subsequently released on bail.
The move came just two days after BP issued a High Court writ pursuing 12 defendants over pounds 2m of bribes allegedly paid on seven contracts worth pounds 80m.
Apart from Thyssen, they include Swiss pumps group Sulzer, several middlemen and Alan Owen, a former senior executive in BP's procurement division based at Harlow in Essex, who it alleges was bribed to supply confidential details on competing contract tenders.
British Steel, Weir Group and Hunting were among UK firms who lost out on lucrative deals because of the alleged activities of the self-styled "information brokers" and Mr Owen.
Two of the middlemen, Polish-born Josef Szrajber and Italian businessman Paolo Sorelli, were jailed in 1993 in a series of convictions gained by the Serious Fraud Office into information brokers' activities.
Thyssen, BP claims, was one of the chief beneficiaries, winning three contracts from the alleged conspiracy, including a pounds 50m export pipeline for the giant Forties oil field.
BP alleges Thyssen paid pounds 1.4m of kickbacks on that deal alone. The money, it claims, was shared via secret Swiss bank accounts and a Panama-registered firm between Messrs Owen, Szrajber, Sorelli and another Swiss-based associate, Walter Dettwiler.
Thyssen acted as agent on the deals for Mannesmann, another German engineering giant in which it has a 25 per cent stake. Mannesmann itself was banned from the Norwegian sector of the North Sea over a similar corruption case involving state-owned oil firm Statoil in 1992.
A Statoil engineer was jailed for two years in 1995 after receiving over pounds 500,000 in bribes. The trial of a Mannesmann employee has still to come to court.
This weekend, Thyssen admitted it had used "consultants" to help gain deals, but rejected BP's charges.
"In the view of Thyssen (Stahlunion), BP has no claims against it," spokesman Dr Wolfgang Kruger said.
"Thyssen Stahlunion also emphasises that in commissioning the consultant to obtain market and competitive intelligence data in this instance, this was neither an inducement to commit any criminal offence ... not certainly one to bribe BP employees."
BP has yet to serve the writs on Thyssen and Sulzer while it prepares translations.
It is also trying to trace Mr Sorelli, who left for Switzerland shortly after his release from prison in September, 1994.
Mr Szrajber and another middleman, Jim Lillie, have been served, however, and plan to fight the case.
"As far as Jim Lillie and Szrajber are concerned, their intentions are to defend the writ," said their joint solicitor, Andrew Blatt of small east London law firm Murdochs.
Arrayed against them is the full might of BP's in-house resources, plus top City law firms and leading counsel and a rack of evidence from the 1993 criminal trials.
Mr Lillie, BP alleges, acted as an agent for Sulzer in winning two deals. This weeken a Sulzer spokesman in Geneva said it would await the writ before deciding its stance. The Swiss parent and two UK subsidiaries are among the 12 defendants,
Apart from the huge Forties deal, BP's 120 page writ seeks compensation and damages for alleged conspiracy on six other North Sea deals in its Miller, Bruce and Gyda fields.
The allegations include:
pounds 33,000 commission payment improperly made by Sulzer to middlemen to win a pounds 2.3m compressor deal
pounds 69,000 paid by Sulzer on a pounds 1.5m pump contract
pounds 428,000 from Thyssen on a pounds 23.8m pipeline contract.
pounds 28,000 paid by Japanese trading house Marubeni for information on a pipeline deal
pounds 78,000 paid by Thyssen on a pounds 1.5m pipe deal.
pounds 25,000 paid by Japanese trading house Itochu on a pounds 870,000 pipeline casing.
An Itochu employee was cleared on corruption charges in 1993 after claiming he only inherited established practice and did not believe he was acting dishonestly.
The trial of a Marubeni executive was cancelled after he fled to Japan while on bail.
The BP writ also alleges that Humphries & Glasgow, an firm of engineering consultants, was also intimately involved in the scam. An H&G employee was also convicted in 1993 on corruption charges involving contracts for the Channel Tunnel.