Wellcome Trust director Mark Walport said: 'Patients are overwhelmingly in favour of the electronic record. It's not always possible or appropriate to ask for their consent.'
Professor Carol Dezateux from the University of London's centre for paediatric epidemiology and biostatistics said: 'People don't want to be overburdened.'
She stressed that ethnic minority patients do not consent as often as other groups but have some of the most pressing health needs for which research using the data was vital.
It is unfair to make researchers 'jump though hoops' just because NHS managers are naturally 'risk-averse', she added.
The electronic records system would store patients' medical history on a central database accessible to clinicians in different health settings and around the country.
It will come in two forms - the 'summary' record, with brief details such as allergies, and a 'detailed' version with full clinicians' notes.
In previous evidence sessions, patient groups voiced concerns that their confidentiality would be eroded if records were passed on for research purposes. A legal professor also claimed it would break European law unless total anonymity was kept.
At the latest hearing last week, Doug Naysmith MP asked the researchers: 'Aren't you being cavalier and a touch arrogant?'
But Professor Simon Wessely of the Academy of Medical Sciences said: 'There is a legal framework that safeguards patient privacy. People aren't aware of these systems.' He said people often quoted the Data Protection Act saying it did not allow secondary use of data, but it actually provides a framework for doing that.
He cited examples of important medical research that would have been rendered impossible if strict rules prohibiting the use of patients' details without their consent.
A later evidence session was attended by Patrick O'Connell, managing director of BT Health, London's local service provider.
He confirmed that the electronic record would not be fully implemented in the capital's hospitals until 2009-10 and that all data would be anonymous.