Doubts are growing over the chemical weapons threat said to be behind a huge anti-terror police raid in London in which a British man was shot then arrested with his brother.

A senior Police officer briefs other police officers in Lansdown road in the Forset Gate area of east London. Questions have been raised in the British press over the circumstances of a huge anti-terror raid here two days ago, in which one suspect was shot, as police continued to question a second man. [AFP/File]

The British press led the chorus of doubts, with a source close to the enquiry telling Monday's Guardian newspaper that the chemical weapons sought in the raid on a house in Forest Gate in east London "might be elsewhere or never existed".

"So far, nothing from the search bears out the intelligence," another Scotland Yard source told the paper.

According to their lawyers, brothers Abul Koyair, 20, and Mohammed Abdul Kahar, 23, vehemently deny any involvement in terrorism after they were arrested during a dawn raid on Friday.

Kahar, who was shot during the raid, was moved on Sunday from Royal London Hospital to Paddington Green high security police station, where he was expected to face questioning for the first time. However, his lawyer Kate Roxburgh said on Sunday evening he was still too weak.

Police have declined to comment on the reports that experts were hunting for evidence of chemical or biological weapons as they continued to search the terraced house.

Neighbours in Forest Gate defended the brothers, who were arrested under the Terrorism Act, describing them as devout Muslims from a Bangladeshi family, and accused police of heavy-handed tactics.

"If the intelligence was wrong, we possibly have egg on our faces,"another anonymous Scotland Yard source said in the Daily Telegraph.

"We have wasted a lot of time, put a lot of people out, one man has been shot and two have been arrested.

"But what was the alternative: that we didn't act? The bomb might not be there but if the intelligence was right, has it been moved?" he added.

According to the best-selling tabloid Sun, the raid by 250 officers could still yield results.

"Although the bomb is still missing some evidence was found at the raided house in Forest Gate to suggest potential links to terrorism," the paper said, citing more anonymous sources.

"The informant is highly regarded and was certain what he saw with his own eyes was a chemical bomb. We are still convinced the information is 100 percent accurate," insisted a source within M15, Britain's interior intelligence agency.

The Daily Mail was much less optimistic of a result, and cited several details of the police operation and enquiry which would be particularly disquieting if the bomb threat were real.

Why were relatives of the brothers allowed to go on holiday to Mauritius so soon after the raid? Why was the Forest Gate area not evacuated? And why did the police not inform Cobra, the anti-terror committee involving ministers, emergency services and security agencies, of Friday's raid?

Questions were also being asked about the shooting and arrests.

A government source told Sunday's News of the World that the shot was fired by Abul Koyair at his elder brother while attempting to grab a policeman's gun.

That theory was denied by the suspect's lawyer Julian Young late Sunday.

"My client accepts he may have shouted but he says he did not struggle and did not cause his brother to be shot".

Scotland Yard refused to comment on the incident which is now subject to an independent investigation.

Young, representing Koyair, added: "My client denies any involvement in the commission, preparation or instigation of acts of terrorism or anything to do with explosives or firearms."

He accused the police of a "cover-up", drawing a direct comparison with the Stockwell tube station shooting last July, when police were heavily criticized for shooting dead innocent Brazilian Jean-Charles de Menezes in the wake of attempted bombings in London.