Complaints about the helpline NHS Direct have risen by nearly 50 per cent since the end of last year, its figures show.
And last month, the number rose to more than twice the target level at the 24-hour healthcare helpline.
In December 2006, there were 1.3 complaints for every 10,000 calls but this figure rose over the next three months, to 1.89 in March.
The target figure is 0.75 complaints per 10,000 calls.
A spokesman for NHS Direct, which receives about 400,000 to 450,000 calls to its helpline each month, said: ‘We have recently gone through a major reorganisation.
‘Our performance has increased significantly in the past few weeks and we would expect the number of complaints to fall after this improved performance.
‘The complaints naturally have a time lag in relation to performance but in a month or two we would expect to see them fall.’
Which? has previously investigated the service provided by NHS Direct and found that it was failing to provide a consistent and effective service.
A survey we carried out last year also found that 73 per cent of people didn’t know the telephone number to call to contact NHS Direct, and 7 per cent said that they hadn’t heard of NHS Direct.
Which? principal policy adviser Frances Blunden said: ‘What we found was that it was a very mixed bag.
‘Sometimes people got through easily and got good advice, but other times people had a long wait, not getting through at all. Particularly at times of high demand, it wasn’t up to scratch.’
Which? wrote to NHS Direct with concerns about its reorganisation – including the fear that it would mean fewer operators answering calls would be healthcare experts.
Frances added: ‘Our feeling was all that could do would be to make things much worse.’