Jeremy Hunt, the culture secretary, has poured further pressure on UK Border Agency staff and civil servants who are planning to strike for 24 hours from midnight on Thursday at Heathrow airport, by appealing to them not to miss "one of the biggest days of their professional career".
As Home Office ministers prepared to seek a last-minute injunction on Wednesday to block the industrial action on the eve of the official opening of the Olympic Games, Hunt asked members of the Public and Commercial Services Union not to strike "when the eyes of the world will be upon them".
He said there were a sufficient number of shifts at Heathrow to maintain "a full immigration desk policy" and insisted the contingency planning for security at the Games, which had seen more than 18,000 military personnel called in, meant the government had enough troops in place or in reserve to make up for the G4S staffing fiasco.
The public could be confident "that absolutely nothing is being left to chance", Hunt told BBC's Today programme.
He said 550 people a day were normally needed at Heathrow to get people through full immigration checks in the shortest time and 584 shifts had been confirmed as covered on Heathrow's busiest day ever. "We can be very confident in the contingency plans we have in place," he said.
Heathrow is predicting that the final big influx of Olympic spectators and officials will mean a record 245,000 passengers will pass through its terminals on Thursday – its busiest ever day.
Heathrow boss Colin Matthews said Olympic arrivals had so far gone well with none of the feared passport queues: "Since 15 July the experience in the airport, including immigration, has been great. If you think of all the staff working so hard and people volunteering to make it a great Olympics, how disappointing tomorrow if that's thrown away."
Hunt told the BBC that for immigration staff, Thursday "is the day the eyes of the world will be upon them and the welcome we will be giving the rest of the world".
He added: "The vast majority of them will be wanting to do a really good job and show what they are capable of. One of the biggest successes of the last few weeks is that queues at Heathrow have been the dog that didn't bark. People have been saying, 'It is going to be a nightmare, we are not going to get people through'." In fact, said Hunt, the action taken by the Home Office to end the queues had been "a tremendous success".
"People have their grievances but surely the day before the opening ceremony of the Olympics is not the right time to pursue them."
Hunt claimed Mark Serwotka, the PCS leader, "must be losing the confidence that what he is doing actually represents the views of the majority of his members. We know only about 10% of his members actually voted to strike."
On Olympics security, Hunt said he did not know whether all the troops called up for Olympics duty would be needed. "We have certainly got enough. We need to know the troops are there."
He refused to criticise G4S guards, blaming the company's executives who failed to honour their contract to supply thousands of staff.
"We were very angry with G4S management but not with the G4S workers," he said. "I just think it's really important we don't demonise them, because they are part of the mix."
Hunt will on Wednesday watch the first sporting action of the games – a women's football match between Team GB and New Zealand in Cardiff. He dodged a question on naming a star from the GB team but admitted that "like the rest of the country", he had a "steep learning curve" on the sport.
