Britain dismissed suggestions of a link between the Lockerbie bomber's release and energy deals with Libya, and the head of the US FBI said the move gave comfort to terrorists.

London and Washington have condemned the "hero's welcome" given to Abdel Basset Al-Megrahi on his return to Libya after being freed from a life sentence in a Scottish jail on compassionate grounds because he is dying of cancer.

"The idea that the British government ... would sit down and somehow barter over the freedom or the life of this Libyan prisoner and make it all part of some business deal ... it's not only wrong, it's completely implausible and actually quite offensive," said British Business Secretary Peter Mandelson.

In Washington, FBI director Robert Mueller released an angry letter he sent to Scottish minister Kenny MacAskill, who ordered the release, calling it inexplicable and detrimental to justice.

"Indeed your action makes a mockery of the rule of law. Your action gives comfort to terrorists around the world," Mueller wrote in the letter posted on the FBI's website.

Prime Minister Gordon Brown's office issued a copy of a letter he wrote to Gaddafi on August 20 expressly asking him to refrain from a "high-profile" welcome for Al-Megrahi.

Gaddafi met Al-Megrahi on Friday, embracing him and getting a kiss on the hand in return. The beaming Libyan leader expressed gratitude to Brown and Queen Elizabeth.

"This step is in the interest of relations between the two countries...and of the personal friendship between me and them and will be positively reflected for sure in all areas of cooperation between the two countries," he told Libyan TV.

His son Saif Al-Islam went further, saying that whenever he had met British officials to discuss business, the issue of Al-Megrahi's release was a condition of any deal being struck.

Mandelson said he had met Gaddafi's son twice in the past year and the issue of the Lockerbie bomber had been raised both times, but his release was not tied to business deals.

"It's not only completely wrong to make any such suggestion or insinuation, it's also quite offensive," he told reporters.

Al-Megrahi, 57, is the only person convicted of the bombing, in which a Pan Am jet carrying 259 passengers -- most of them American -- was blown up over Lockerbie in Scotland in December 1988, killing all those on board and 11 people on the ground.

After years of wrangling and sanctions, Libya handed the former intelligence agent over for trial and he was sentenced by a special Scottish court sitting in the Netherlands in 2001. He was freed on Thursday because of terminal prostate cancer.

"In all British interests regarding Libya, I always put you on the table," Saif Al-Islam's newspaper quoted him as telling Al-Megrahi on his return to Libya.

"All the visits of the ex-Prime Minister Blair and the big secret and public work that all the parties entered into was carried out in order to release you. The exploitation of British-Libyan political and trade interests was always done with the aim of releasing Abdel Basset Al-Megrahi."    

European governments including Britain's are lobbying hard for business in Libya as it emerges from years of sanctions. Oil companies such as BP and Shell are among several British firms hoping to make big profits in the desert country.

Britain's Foreign Office flatly denied any link. "No deal has been made between the UK government and Libya in relation to Megrahi and any commercial interests," a spokesman said, adding the release was Scotland's decision.

More than 1,000 Libyans gathered at an airport in Tripoli on Thursday to welcome Al-Megrahi home, cheering and waving national flags, despite the fact relatives of the American victims said they had received assurances there would be no hero's welcome.

In his letter to Gaddafi, addressed<