The CIPD has repeated calls for employers to invest in staff if they are to retain them after the recession.
The warning comes as new figures reveal that more than one-third of workers want to change their careers once the economic crisis is over.
A survey of 3,000 employees by the Chartered Institute of Personnel and Development (CIPD) found that concerns about job security and a lack of opportunities were forcing workers to stay put.
However, 34% admitted they would switch jobs within the next year - in an ideal world.
Claire McCartney, the CIPD's talent and resourcing adviser, said the poor labour market was acting like a dam holding back the normal flow of talent.
"Once job opportunities increase, however, dissatisfied employees will vote with their feet and leave, making it important for employers not to take the loyalty of their people for granted," she said.
"Employers need to be careful to avoid complacency. The recession may keep your best people with you for now, but you need to take the time to focus on building employee engagement by providing employees with clarity around career paths and setting work that is meaningful to them, if you want them to stay put when better times return."
McCartney's comments follow a call to HR from the Institute of Leadership and Management earlier this month, which warned that a failure to prioritise staff engagement could prove costly in the long-term. HR practitioners vowed to make staff satisfaction a top priority to prevent good staff leaving or becoming disengaged.
The CIPD survey found that employees in banking and finance (41%) and construction (40%) were the most likely to jump ship.
And 25% of private sector workers would consider changing sectors, compared with 19% in the public sector and 17% in the voluntary sector.
The most popular areas to move into appeared to be the public and voluntary sectors, with 28% looking for work in community, social and personal services.
Meanwhile, 20% wanted to move into education and 17% were looking for health and social work opportunities.