The coronavirus crisis has created a backlog of more than 400,000 passport applications, say reports.
The BBC said Home Office minister Baroness Williams explained that reduced staffing to allow social distancing meant forms were taking longer to process.
The Passport Office is advising only people going away before September or those travelling on compassionate grounds should currently apply for a passport.
In a written Parliamentary answer about the backlog, Baroness Williams said the Passport Office “continues to operate at reduced staffing levels so its people can continue to socially distance”.
She added: “As part of its contingency arrangements, HM Passport Office is rapidly increasing its capacity for processing passport applications, in line with public health guidance, which will help to ensure it continues to meet the travel needs of its customers.”
As of July 7, the BBC reported, work was under way on about 126,000 passport applications – 31% higher than at the same period last year.
The minister said a further 284,000 applications would “need to be worked through in the coming weeks once initial documentation has been received and allocated”.
This represented an increase of 172% from last year, she said.
Baroness Williams disclosed the scale of the passport backlog in a response to a question by Labour over the delays.
Those applying for new passports will be among the first to receive a blue version, introduced from April after 30 years, following the UK’s departure from the European Union.
Earlier this week, the Telegraph reported that long delays to passport applications were forcing some families to cancel holidays.