Tens of thousands of people have been stopped in the street and searched unlawfully under controversial section 44 anti-terrorism powers, the Home Office has revealed.

Fourteen police forces are urgently trying to find the individuals involved so they can apologise to them after being told by the Home Office that errors had been found in the way 40 separate stop and search operations were authorised since the powers were introduced in 2001.

Nick Herbert, the police minister, said in a Commons statement that the mistake was discovered after a freedom of information request triggered a review of the Metropolitan police's section 44 records.

"The Met identified an authorisation from April 2004 which had not been confirmed by a Home Office minister within the statutory 48-hour deadline for confirmation," Herbert said.

"Subsequent investigations revealed that approximately 840 were stopped and searched in the relevant area during the period of the invalid authorisation."

The Met is urgently considering what steps to take to contact the people involved.

The discovery triggered a Home Office search last month through all the records dating back to the introduction of section 44 in February 2001.

The search revealed that 14 forces had unlawfully used their counter-terror stop and search powers in 40 different operations.

The Home Office said that in most of the cases authorisations were issued for periods beyond the 28-day statutory limit for each operation or were not signed off by ministers within the statutory 48-hour deadline.

The disclosure is another major blow to the police use of section 44 of the Terrorism Act 2000, under which anyone can be stopped in a specific area without any need for suspicion that an offence is being committed.

The powers were used to stop 148,798 people last year and have been used repeatedly against peace protesters and photographers.

In a landmark judgment in January the European court of human rights ruled that the blanket use of section 44 across the whole of London was unlawful. It criticised the lack of legal safeguards against abuse in the way the operations were authorised.

Coalition ministers stressed today that they had repeatedly criticised the arbitrary use of section 44.

The home secretary, Theresa May, has said that the use of such counter-terror powers will be reviewed, with safeguards introduced to curb excesses.

Herbert said: "I am aware there is considerable concern about the operation of section 44 stop and search powers going beyond these authorisation errors.

"The government is committed to a wider review of counter-terror legislation, including the operation of section 44 stop and search provisions.

"Whilst I take some reassurance from the fact that no errors have occurred since December 2008, when the authorisation process was tightened, I want to assure the House that there will be utmost vigilance in future.

"It is with the need for this in mind that I have instructed Home Office officials unconnected with the administrative process to conduct the internal review of procedures."

The Met and City of London police have made the greatest use of stop and search, with 10 of the 40 illegal operations being in London. Thames Valley police were responsible for six of the illegal operations, Sussex five and Greater Manchester three.

Corinna Ferguson, a lawyer for Liberty who acted in the successful court of human rights challenge, said: "We are grateful to the government for making these blunders public, but they merely highlight the ongoing dangers of secret stop and search authorisations.

"This is one of many objections to a power that has been found unlawful in the court of human rights and has been more of a hindrance than a help to anti-terror policing."

Senior police officers defended the continued use of section 44.

Chief Constable Craig Mackey, the Association of Chief Police Officers (Acpo) head for stop and search said: "Powers to stop and search can play an important part in keeping our communities safe from terrorism but should always be used in a proportionate way, recognising the critical need to retain local confidence.

"Where mistakes have been made in the application of these powers it is vital that we learn from them.

"In December 2008 the use of Section 44 was reviewed through Acpo and the National Policing Improvement Agency and practice advice issued to forces, supported by training. No errors have been found in the application process since that date."

He said each of the forces concerned, along with the Home Office, would "look at the implications where mistakes were made and Acpo will support that process".

Mackey insisted that used correctly, section 44 powers could create a hostile environment for terrorists to operate in and help protect the public.

Just-released figures for the use of Terrorism Act 2000 powers show there were 148,798 stop and searches under section 44 in 2009, a 40% fall over the previous year.

A total of 688 arrests were made as result of these searches, an arrest rate of 0.5%.

The Home Office statistics reveal there were 207 terrorism arrests in 2009 compared with 174 the previous year. The 207 arrests led to 56 people being charged but only 23 of them for terrorism-related offences. The rest were charged with non-terrorism crimes.

Ninety-five people were released without charge, and alternative action – mainly cautions or immigration proceedings – was taken against the remaining 56.

The figures show there were 131 people in prison for terrorist or terrorist-related offences on 31 December 2009.