Desperate teachers have launched a campaign to get Prime Minister Gordon Brown to change rules that mean they lose their qualifications if they fail to find a full-time staff job after four terms.
Hundreds have signed a petition on the Prime Minister's website complaining about the 16-month limit on working in supply for new staff.
If these teachers have not found a full-time job they face a ban on working supply shifts in the state sector.
Unions say the rule is a "betrayal" of the thousands of graduates lured into the profession with the promise of a career, only to find scarce employment once training has finished. A recent Training and Development Agency for Schools (TDA) survey found only a third of newly qualified teachers (NQTs) in some areas got permanent jobs this year.
NQTs used to be able to take on supply work for five years, but they now only get an "allowance" of 16 months. If they are desperate to continue to supply after this deadline they have to apply to any local authorities where they want to work for an official extension.
The petition - which reads, "We the undersigned petition the Prime Minister to abolish the 16-month limit for non-inductible supply teaching" - has been signed by 208 people at time of going to press.
"I went on supply two weeks ago and found another NQT," a teacher using the alias "mfacchinei" wrote on the TES forums. "We started talking about this rule and she was almost in tears, as her time was running out.
"I told her to ask for an extension but she replied she already did and this, too, was about to finish. She told me she had applied to almost every job advertised in the North West, with no luck. For every job there are at least 50 applicants.
"It is so unfair that unqualified cover supervisors are offered supply jobs and NQTs are threatened with this unfair rule."
Another teacher affected, going by the alias "historygrump", said: "I feel that the rule is in breach of the Human Rights Act, in that the Government is denying the right of qualified teachers from working, not on the grounds of being a criminal, but on the grounds of being unable to find a full-time role."
John Bangs, head of education at the NUT, has called for the rule to be changed, and for the TDA to review job availability.
"The TDA needs to be more responsive to changing employment trends," he said. "They take justifiable pride in solving the teacher shortage and it would be a shame for this to be overshadowed by unemployment. This would also lead to those teachers they lured into the profession without jobs feeling betrayed."
Officials say the rule exists to make sure that all new teachers complete the year-long induction period in a school, where they are given a mentor and sent on training courses.
However, campaigners are also frustrated that there is no limit for those who qualify as a teacher but then fail to work at all in the profession.
A TDA spokeswoman said the 16-month rule had been adopted after a consultation period.
"Supply cover is explained to NQTs by their training providers, and the TDA sends them an information pack when they receive their QTS certificate from the General Teaching Council for England," she said. "This outlines their entitlements and reminds them that there are limits to the short-term supply that can be undertaken."
The petition can be found at http:petitions.number10.gov.uk16monthsupply?signed=f78eff6.a92e4d.