BAA HAS accelerated its redundancy programme at Heathrow's T5.
Union officials were told this week that more than 400 workers will be let go between now and the end of January.
One site source said: 'It seems BAA has decided to step things up on the redundancy front.
'For the past few weeks there have been problems with not enough materials on site and people with nothing to do.'
Last week Construction News revealed how BAA was to introduce a 'Focus on Finishing' programme after fears that productivity was dropping.
A BAA spokeswoman said: 'The construction phase largely ends in September next year. Consequently the workforce will be reduced over the course of the next nine months.
We will look to redeploy workers wherever possible.'