Police are trying to trace a gang of British Muslims who are thought to have returned to plot terror attacks in Britain after being trained abroad for more than a year by al-Qaeda, Nine Britons, all said to be in their twenties, were among a group of 12 Western recruits groomed by al-Qaeda at a secret camp near the Afghan border to set up new terror cells in London and other Western capitals.

Police do not know the real identities of this gang, who are known as the “English brothers” because of their shared language. As well as nine Britons, they include two Norwegians and an Australian who were smuggled into the Waziristan tribal region in Pakistan in October 2005.

They are believed to have been under the command of an al-Qaeda veteran suspected of training some of the Britons accused of the alleged plot to blow up passenger planes flying to the US from Heathrow airport in the summer.

The intensive manhunt for the “English brothers” was revealed to The Times as the alleged British mastermind of the Heathrow plot spoke for the first time as he appeared yesterday in a court in Pakistan on separate charges. Outside court, he vehemently denied any role in plans to bomb up to ten transatlantic flights.

Rashid Rauf, 25, from Birmingham, had not been seen in public since his arrest in August by Pakistani intelligence chiefs, who claimed that he was the key figure in the foiled operation.

Talking to The Times inside a crowded court in Rawalpindi, Mr Rauf, who was manacled hand and foot, said of the accusations: “The charges are all fabricated. It is an injustice, there is no evidence against me.”

A tall, lean figure with a long unruly beard and his head covered by an embroidered shawl, Mr Rauf smiled when asked if he fears being returned to Britain to stand trial. Senior officials in Pakistan have told The Times that diplomatic efforts are under way to transfer Mr Rauf to Britain, where detectives want to question him about the alleged Heathrow plot and possible links to the 7/7 London suicide bombers.

A security source in Islamabad said last night that the transfer could happen “in weeks” even though there is no formal extradition treaty between the two countries. Mr Rauf, who is facing charges in Pakistan of forgery and possessing fake documents, is due back in court on January 5.

Terrorist charges against him were dropped by a judge this month and his case was transferred to another court.

There are claims that British police wanted the authorities to hold on to Mr Rauf while they prepared a case. One official in Islamabad said: “British police could not complete investigations in the 28 days they had to detain a suspect.”

Mr Rauf’s capture in the summer was believed to have triggered arrests across Britain and forced ministers to go public on claims that British-born terrorists were about to detonate liquid explosives on aircraft leaving Heathrow for US cities.

Thousands of passengers were stranded at British airports and flights grounded. Eleven men, most of Pakistani origin, have been charged in Britain with conspiracy to murder and preparing an act of terrorism. Yesterday, Mr Rauf’s lawyer, Hashmat Habib, said that the Heathrow plot was “a fake and was used [to] boost up the political position of Tony Blair and George Bush”.

British police have already said they want to interview Mr Rauf about the murder of his uncle, Mohammad Saeed, 54, who was stabbed close to his home in Alum Rock, Birmingham, in 2002. Mr Rauf denies any involvement in the killing.

Police are keen to learn whether he met two of the 7/7 bombers, Mohammad Sidique Khan and Shehzad Tanweer, who are known to have visited Pakistan shortly before they and two other British Muslims blew up three Underground trains and a bus, killing 52 people in London in July 2005.

The alert over the whereabouts of the “English brothers” came as Sir Ian Blair, the Metropolitan Police Commissioner, cautioned about “an unparalleled and growing threat of attack”. He said that the terrorist threat was “far graver” than any posed during the Second World War, the Cold War or IRA campaigns.

Sir Ian, speaking on the Today programme on BBC Radio 4, said that he had no specific intelligence about an imminent attack but the threat was “ever present”.

Security chiefs fear the orchestrators are likely to be British Muslims who have been given training abroad. The “English brothers”, regarded as “too valuable” to take part in suicide attacks, have slipped back to tutor homegrown recruits.

Intelligence sources in Pakistan said that the men are reported to have joined Taleban and al-Qaeda fighters in Afghanistan in attacks on Nato troops. The sources told The Times that the “brothers” were given religious indocrination as well as lessons on how to assemble suicide bomb vests and improvised explosive devices.

The sources are reported to have been escorted to the al-Qaeda camp by Adam Gadahn, a Californian indicted by the US authorities as an al-Qaeda terrorist, who introduced the “brothers” to their tutors.

Times Recommends

• It’s only Brits who don’t appreciate me, says Blair
• Party’s over for Greek graspers
• White House tightens security for Xmas marathon