Victim Support urged the Government and police forces across England and Wales – almost all of which saw a record number of offences last year – to take the crime seriously.
Home Office figures show Hampshire Constabulary recorded 794 blackmail offences in the year to March – up from 547 in 2020-21, and the most since comparable records began in 2012-13.
Across England and Wales, 22,000 such offences were recorded in 2021-22 – more than double the number before the coronavirus pandemic in 2019-20, and also a record.
The crime – which is punishable by up to 14 years in jail – is one of the fastest growing over the last decade.
Victim Support said the rise could reflect more crimes or victims feeling more empowered to come forward, but warned many still choose not to as they feel embarrassed.
Diana Fawcett, chief executive of the charity, said: “This steep rise in reports of blackmail is seriously concerning – with only 1% of cases resulting in a charge, we risk victims losing trust in the criminal justice system.
“It is essential victims of blackmail are given practical and emotional support to help them recover and seek justice.
"Police forces and the Government must take this crime seriously and get to the bottom of why we’re seeing this increase.”
Although the figures do not break down the type of blackmail carried out, the National Crime Agency views "sextortion", or webcam blackmail – where victims are tricked into performing sexual acts on video – as a growing threat.
And the Revenge Porn Helpline, which supports those who have suffered intimate image abuse, said it was their most reported issue in 2021.
Zara Ward, a senior practitioner at the service, said: "In many of our cases we are only seeing the tip of the iceberg and so many of these instances go unreported because the scammers have a huge impact on their victims, and it can lead to a lot of victims remaining silent."
She said the pandemic drove much of people's daily communication online, including relationships, and a lot of scams now begin on dating apps or social media.
The National Police Chiefs’ Council said a rise in blackmail crimes is largely down to improvements in recording.
It encourages anyone who has been a victim to report it to the police – where they will receive continued support – and not give in to demands.
Separate figures show that of the 20,360 blackmail investigations closed nationwide in 2021-22, just 1% resulted in a charge or summons, and 59% with no suspect identified.
Of these, 755 were concluded in Hampshire, with 79% resulting in no suspect being identified, 19% abandoned due to evidential difficulties and less than 1% with a charge or summons.
A Home Office spokesperson said: “We are supporting police by funding crime prevention measures, including equipping police with better technology to help catch more criminals.
"We are working with partners across the criminal justice system to increase the number of cases being charged and prosecuted.”