Many primary care trusts in England have cut their budget for stop smoking services, according to figures from the Conservative Party.
Around 70% of smokers are reported to want to quit
A survey found that 44 of the 115 PCTs surveyed had cut or frozen funding during this financial year.
A further 12 PCTs had raised their budgets by such a small amount that it amounted to a real terms cut.
The government said spending on smoking cessation had risen, and great strides had been made in helping people quit.
However, the Conservatives said the figures showed that NHS Stop Smoking services were deteriorating - and pinned the blame on the financial problems of the health service.
The party has calculated that the PCTs which are cutting their stop smoking budgets in real terms in 2006-07 finished the last financial year with an average deficit of over £3.4m.
In contrast, among PCTs which are increasing their stop smoking budgets, the average deficit was £2.9m.
Government figures show that over 17,000 fewer people quit smoking through the NHS between April and September 2006 than in April to September 2005.
Andrew Lansley, the Shadow Health Secretary, said: "One in every 20 quitters relies on the NHS stop smoking service, but these cuts mean that this support will become increasingly scarce.
"These cuts are coming just before the introduction of the smoking ban, and the once-in-a-lifetime opportunity it represents to encourage thousands of smokers to quit.
"It is an outrageous example of Labour's mismanagement and lack of concern for public health.
"What is the point of anti-smoking campaigns if they can't be followed up?"
The Department of Health said £56m was allocated to the NHS for smoking cessation services this year - up from £51m a year ago.
A spokesperson said: "We know that NHS stop smoking services have been hugely effective in helping people quit.
"Between April 2005 and March 2006 nearly 330,000 people remained quit at the four week follow up by NHS stop smoking services.
"We have already exceeded our three-year target to help 800,000 people quit by 2005/06, and still more and more people are successfully kicking the habit."
The spokesperson said there had been huge strides in tobacco control in England since the publication of the White Paper Smoking Kills in 1998.
These included a ban on advertising, and more hard-hitting warnings on packs.
"Since Choosing Health, in 2004, we have done even more - measures are coming in to further tackle underage smoking, proposals for the introduction of graphic pack warnings, a new strategy to tackle smuggling was launched and this summer will see the introduction of comprehensive smoke-free legislation."