By Matt Chorley, Mailonline Political Editor Thousands of families' holidays are under threat from a strike yesterday by Passport Office staff, the government warned. Unions staged walkouts at offices across the country in a dispute over staff shortages which they claim have led to a serious backlog in processing applications this year. But as social media was flooded with complaints about the walkout, the Home Office warned the industrial action at the height of summer will 'inconvenience' people and 'jeopardise' their holidays. Scroll down for video Members of the PCS union form a picket line outside a Passport Office in Victoria in central London
@highlight
PCS union staged walkout in protest at staff shortages and pay dispute
@highlight
Huge backlog of 30,000 passport applications sparked public outrage
@highlight
Home Office warns industrial action will threaten people's summer holidays
@highlight
Social media flooded with complaints from people whose holidays are ruined
@highlight
Tory party chairman Grant Shapps said: ‘Ed Miliband must condemn these union bullies, who are intent on causing misery for millions of families'
A spokesman said: ‘We are disappointed the @placeholder has called this strike given that HMPO has been in discussions with the union on their issues of concern.