There has been a “temporary increase” in demand for new passports ahead of more than 1,000 Passport Office workers starting five weeks of strike action.
The Home Office confirmed a rise in applications but said the amount was “close” to levels estimated.
It said there were currently no plans to change its 10-week guidance for passports to be processed and sent out.
Members of the Public and Commercial Services union are striking until 5 May in a row over jobs, pay and conditions.
Workers will walk out across England, Scotland, Wales and Northern Ireland from Monday.
The PCS union has warned of delays to applications and the delivery of passports in the run-up to summer.
To mitigate the impact on services, the Home Office is deploying staff who have previously worked in Passport Offices during busy times of year.
It is understood people who require a passport on compassionate grounds for urgent travel will still be able to get one. However, there will be a reduction in the amount of appointments available for other urgent services.
The union has said the walkouts are being targeted to cause mass disruption and involve members working in departments which examine passports – more than 1,300 people.
The offices affected are Durham, Glasgow, Liverpool, London, Newport, Peterborough, Southport and Belfast.