The Home Office has set out details of how people facing delays to their passport renewal can get it fast-tracked for free.
The temporary offer will apply only to UK residents who are due to travel in the next seven days and where the delay is deemed to be no fault of their own.
It is part of plans announced by Home Secretary Theresa May to deal with a backlog of 30,000 applications.
Labour says the home secretary must apologise for the "shambles".
But the BBC's political correspondent Ross Hawkins said ministers believed they had nothing to apologise for - following the highest demand in applications for 12 years - and were sorting the problems out.
Home Secretary Theresa May told MPs on Thursday that people with an "urgent need" to travel would have their renewal application upgraded to the fast-track service for free.
It normally costs £103 for a fast-track passport renewal, which is delivered to your home within one week of your application being accepted.
The Home Office has now published details of how the new scheme will work on its website. To qualify:
- People must be booked to travel within the next seven days
- The Passport Office must have had their application for longer than three weeks, the standard processing time for renewals
- Delays to their applications must be "through no fault of their own". If someone has filled in their form incorrectly or not provided the right information they will not benefit
- The scheme takes effect immediately but is temporary and is not retrospective
- Adults applying for their first passport will be excluded unless they have valid compassionate grounds for needing to travel
In a statement, the Home Office said Mrs May recognised the "understandable concerns" about delays and was "determined to do everything possible, while maintaining the security of the passport, to speed up the system".
Among other emergency measures announced in recent days, those applying for passports overseas on behalf of their children will be given special travel documents.
New passport applicants who are required to have a face-to-face interview are being turned away from the agency's Durham office and directed to other sites in the North of England while no further interviews are being scheduled in London for the time being.
A Home Office spokeswoman said this was normal practice during busy times.
Mrs May and other Home Office ministers have blamed the problems at the Passport Office on a surge in applications, attributing it partly to growing public confidence about the economy.
But critics have blamed the closure of seven overseas passport processing centres, which has seen all the paperwork they used to handle now processed in the UK.
Labour says the government should have anticipated the spike in demand.
Three million passports have been issued for UK customers in 2014, including more than one million since the start of April, while about 465,000 renewals and first-time passport requests are currently in the system.
In its annual report last year, the Passport Office forecast that changes to the way overseas applications were handled would lead to it dealing with 350,000 more customers.
Responsibility for dealing with overseas applications was changed from consulates and embassies to a UK-based online system in March, intended to provide better value for money and more "consistency" of service.
Mrs May told MPs on Thursday that she had ordered an internal review into how the agency could be run more efficiently, saying it was not just a question of "throwing more staff at the problem".
In the longer term, she said the passport office could be stripped of its agency status and brought directly under Home Office control "in line with other parts of the immigration system".
Passport Office chief executive Paul Pugh - who will be questioned next week by MPs on the Commons Home Affairs Select Committee - said there had been "exceptional" summer demand but that extra staff had been brought in to handle applications.
Labour have accused ministers of incompetence, saying they initially refused to acknowledge there was a backlog despite MPs being inundated with complaints by their constituents.
Speaking on Thursday, shadow home secretary Yvette Cooper said it was a "sorry shambles".
Unions have said ministers had gone "to extraordinary lengths" to deny the scale of the problems, which they say are a result of staff cuts since 2010.