More than 100 borders staff were rehired after leaving the UK Border Agency or Border Force, officials have said.
Too many borders staff were cut too quickly and more had to be recruited to meet demand, Dame Helen Ghosh, the most senior civil servant in the Home Office, admitted.
Fuelling concerns staff were pocketing redundancy payments and then returning to claim a salary, Dame Helen told MPs that the average payout for staff leaving the UK Border Agency (UKBA) is £34,000, rising to £54,000 for those leaving the Border Force.
Permanent secretary Dame Helen said many of those who returned after six months were brought back to help cope with the extra demand caused by this summer's Olympics or with pressure points at overseas posts.
Her comments came after Whitehall's spending watchdog warned in July that the troubled UKBA cut too many staff too quickly and was having to hire extra people and increase overtime to meet demands.
"Did we lose people too quickly? In retrospect, of course if you look at the issues about increasing passenger numbers, concerns about customer service, perhaps we would not have moved quite so fast as we did," Dame Helen said.
But she added that by the end of the financial year the organisation would have effectively broken even on those taking voluntary departure. She also denied there were "widespread warning bells" before the cuts were made.
"On the Border Force side, the new policy focus on 100% checks post-January, the increasing focus on the service we were giving to customers - in retrospect, had we known both of those things, we might not have let quite so many people go," Dame Helen said. "But of course they might not have been people in the right place."
Giving evidence to the Commons Public Accounts Committee (PAC), Dame Helen said 84 people who had been previously employed in some way by the UKBA or Border Force had been rehired. A further 20 people were re-employed through agencies, she added.
Margaret Hodge, the committee's chairwoman, said the fact the Olympics were taking place in London over the summer was "no big surprise" and the MPs would be commenting on the situation in a forthcoming report.