The figure is 100,000 times more than previous estimates and could be even higher due to under-diagnosis and as yet undiscovered faulty genes.
'The reality is that there are hundreds of thousands of people across the UK who are unaware that they could be at risk of sudden death,' said Professor Sir Nilesh Samani, BHF's medical director.
He added: 'If undetected and untreated, inherited heart conditions can be deadly, and they continue to devastate families, often by taking away loved ones without warning.'
A child of someone with certain genetic heart conditions has a 50 percent chance of inheriting it themselves. In the UK, around 12 people aged 35 or under die each week from sudden cardiac arrest with no explanation.
Last April, former England and Nottinghamshire cricketer James Taylor was forced to retire at the age of 26, because of a rare but serious genetic heart condition – arrhythmogenic right ventricular cardiomyopathy (ARVC), which is caused by a mutation in one or more genes.
'It is safe to say that being diagnosed with ARVC was the toughest and scariest week of my life,' Taylor told The Guardian. 'I never would have thought it would happen to me. I was 26 years old and playing cricket for England but my condition meant that I was at risk of sudden death from a cardiac arrest.'
'I was lucky as my condition was detected early and despite having to give up my career, with medication I can lead a relatively normal life,' he added.
Research has helped to discover many faulty genes that cause inherited heart conditions. 'Thanks to the public's kind support, our researchers have discovered some of the genes responsible for these frightening conditions but there is still much to do,' said Professor Samani.