Responding to the SFO's announcement, BAE Systems said it was prepared to go to court to settle the allegations.

In December 2006, the SFO dropped an investigation into BAE over allegations that it bribed Saudi Arabia officials to secure an arms deal after Tony Blair, the British prime minister at the time, said the probe threatened national security.

However, the SFO's investigation continued into bribery allegations related to BAE sales to the four countries involved in Thursday's decision.

Massive fine

Lawyers believe BAE, whose shares were down 4 per cent in early trading in London on Thursday, faces penalties and fines that could run into hundreds of millions of pounds if it is found guilty in any criminal proceedings.

But they caution that such cases are notoriously difficult to prove.

George Brown, a partner in global regulatory enforcement at law firm Reed Smith, said: "The UK authorities will want to show that there is some sort of comity in relation to the way in which one deals with international corruption and will want to follow the lines of Germany and the US."

Brown noted that it was much easier to convict individuals of bribery or corruption than companies.

"To get a prosecution of the company you have to prove that the person who is the controlling mind and body of the company was involved in making the decisions," he said.

Howard Wheeldon, a senior strategist at BGC stockbrokers, said Britiain's Anti-terrorism, Crime and Security Act 2001 extended UK corruption law to include bribery of overseas officials, but that if the case referred to events before that date it would be "very difficult for the SFO to build a case".

Late last year Siemens, the German engineering conglomerate, agreed to pay just over $1.3bn to settle corruption probes in the US and Germany, ending two years of uproar that rocked the company.