Assaults on paramedics working for Gloucestershire's ambulance service have almost doubled in 12 months.

The figures, released by the NHS, have been condemned as "totally unacceptable" by health bosses.

They reveal 44 Great Western Ambulance Service (GWAS) workers were attacked while on 999 calls in the last financial year, compared to 23 assaults in 2007-08.

One paramedic, who wishes to remain anonymous, has spoken about the night when, as he was trying to help a caller, he was assaulted.

He was punched in the chest by his assailant –- a regular caller to the 999 service – after attending his home.

The attacker, who had previous convictions for attacking ambulance staff, was jailed for six months for the assault.

The paramedic said: "I always considered I had a pretty good radar for picking up when this sort of situation was developing. In nine years of pre-hospital care prior to this, I had not been subjected to physical assault. This incident brought home how, on the face of it, the person was extremely unlikely to become violent – but it shows it is not always your drunken, Saturday night individual who is liable to behave like this.

"Following the attack, I am more conscious of the dangers when I attend 999 calls as a solo responder. I have lost faith in my ability to judge situations and be aware of when they might suddenly become more difficult."

The GWAS serves Gloucestershire, Wiltshire and the former county of Avon – now largely Bristol.

Its chief executive, David Whiting, said: "It is totally unacceptable for our staff to be subjected to assault – physical or verbal – in the course of their life-saving work.

"While 44 physical assaults, out of more than 233,000 emergency responses our staff attended last year, may be fairly low, it is still 44 too many.

"The experience of our paramedic who has spoken out shows it is not just the physical attack that is damaging. It has an ongoing effect on him, his colleagues and family and his confidence in continuing to provide the best care.

"I am determined that anyone who does attack any member of my staff is subject to the full force of the law."

Ian Britton, GWAS security specialist, said: "We urge staff to report [assaults] if they happen and we are working to ensure this process is as smooth and straightforward as possible."

GWAS paramedic Chris Hewett, who is Unison branch spokesman, said: "Unison condemns any attack on ambulance staff. We continue to work closely with GWAS to prevent attacks and to support members who are victims of assault."