30 million could be in work by 2015
A study of the labour market by the Chartered Institute of Personnel and Development (CIPD) said that continued growth in employment was likely in 2013.
But the report also warned that excess capacity had built up in some firms as employers held on to skilled and talented staff.
This could lead to weaker employment growth even if the economy picks up, said the CIPD.
Latest figures showed there were 29.6 million people in employment in the quarter to October, an increase of almost half a million on a year earlier.
Mr Beatson said: "The jobs enigma, of strong growth in private sector employment in the absence of sustained economic growth, has been one of the most mystifying economic features of 2012, and if 2012 proved an enigma, the labour market appears equally difficult to pin down for 2013.
"Although the flexibility of the UK labour market is an important factor, the popular focus on under-employment as a major factor in explaining rising overall employment seems overplayed.
"While there are undoubtedly significant numbers of people working fewer hours than they would like, and this is an issue that merits further investigation and consideration by policy makers and employers alike, the numbers have not increased significantly this year, making it a poor explanation on its own for the 2012 jobs enigma.
"On balance, there are likely to be further increases in employment. Rising employment alongside muted growth indicates that employers have significant reserves of skilled labour capacity on which to call to support growth."
© 2012 Press Association