The latest figures from the Information Centre for health and social care show that the number of people successfully giving up smoking for four weeks fell from more than 200,000 in 2005 to around 180,000 in 2006.
Deborah Arnott, chief executive of anti-smoking group ASH, said the figures were worrying because NHS quit-smoking services were crucial in the drive to reduce smoking among the most disadvantaged groups in society.
This problem was underscored by the figures, which show that smoking rates are falling fastest in the affluent South East and slowest in the North West.
Ms Arnott said: 'If we are not getting to those people and they are not making best use of resources, then we have a problem.'
The funding of NHS smoking cessation services has been surrounded by controversy for some months.
In May, HSJ reported on a link between the drop in Department of Health funding for national anti-smoking advertising and a subsequent fall in the number of quitters.
The latest figures, which cover April to December 2006, confirm this fall in the number of people giving up smoking.
In March, the Conservative Party released a survey showing that 56 of the 115 primary care trusts they had surveyed had cut their quit-smoking budget.
Ms Arnott said: 'Central government funding has held up well, but it has not been ring-fenced and it has not translated down to the local level.'
A DoH spokesperson said: 'Adult smoking rates in England are the lowest on record and indicate that the government is on track to meet the overall target of 21 per cent smoking prevalence in 2010.'
She added that a major public relations and advertising campaign is under way in the run-up to the introduction on 1 July of legislation banning smoking in enclosed places in England.
In addition, she said the DoH had increased funding for local NHS stop-smoking services by nearly 10 per cent over the last two financial years.