The home secretary has asked police to explain why a mistake was made in the government's version of what happened on the day of the London bombings.
Fifty-two people were killed in the bombings
John Reid revealed the time at which the bombers left Luton station to head to London was wrong in the official "narrative" of 7 July 2005.
He told MPs the error did not seem to affect anything else in the account.
But he acknowledged it might cause concern and said he had asked police for a report about the discrepancy.
The official account, published earlier this year, said the four bombers had left Luton train station at 0740 BST on 7 July.
However, it has now emerged that was inaccurate - they actually left at 0725, but the account was right in saying they arrived at King's Cross station at 0823.
Mr Reid said the discrepancy came to light at the end of last week, when police pointed out the inaccuracy.
The bombers went on to attack London's transport network in four bombings - killing 52 people and injuring nearly 800.
Mr Reid was speaking on Tuesday during a Commons debate on the annual report of Parliament's Intelligence and Security Committee.
The home secretary, who has rejected calls for a public inquiry, criticised inaccurate press reports about what intelligence services knew about the bombings.
The attacks had not been the result of an intelligence failure, he argued, saying it was understandable why two of the bombers had only been on the periphery of the security services' investigations.
Shadow home secretary David Davis praised the work of the intelligence agencies.
But he urged the government to press ahead with allowing phone-tap evidence to be used as evidence in British courts - something ministers have already promised to review.
Mr Davis said all the potential obstacles to the move could be overcome.
"More than a year after the attacks we are still in the absurd position where intercept evidence from foreign jurisdictions is admissible in our courts but evidence from our own services is not," he said.
The government has previously resisted the measure for fear of revealing the source of phone-tap evidence.
Mr Reid said the Home Office was examining two possible ways of using the evidence.
A report would be given to ministers in November, he said.