The move follows the announcement that giant Canadian manufacturer Bombardier, the leader of the Linc consortium, intends to buy Adtranz, DaimlerChrysler's rail business, which is part of the Metronet consortium.
Both consortia have been shortlisted for the public-private partnership contract to refurbish the Bakerloo, Central and Victoria deep lines. They are also understood to be competing to refurbish the Tube's sub–surface lines.
A spokesperson for the mayor's office said there was concern that one company would be involved in two competing bids. The spokesperson said: "The mayor is deeply concerned about this issue. This merger appears to reduce competition for the London Underground refurbishment and we are looking into it."
Livingstone has been a fierce opponent of PPP for the Tube, recently calling the bidders "the worst scum of modern British capitalism".
A source close to LU said the impact of the merger was unclear as it may not take place before the Tube contracts are awarded, but added: "I would be very surprised if the government didn't decide to take a serious look at it, never mind Livingstone."
I would be very surprised if the government didn’t take a serious look at it, never mind Livingstone
London Underground Source
A spokesperson for Metronet said: "We are evaluating the effect of the move on our PPP bids. We are looking at the issue to ensure there is no conflict, but we are confident it won't affect our bid. We're determined to succeed."
Linc was unavailable for comment.
The DETR declined to discuss the comments made by Livingstone's office but said that by the time the merger deal received regulatory approval, the contracts for the refurbishment would have been let.
A spokesperson said: "We are reviewing the situation and will keep a close eye on the moves by monitoring things. But commercial moves of this kind are not unusual and there are well-established procedures involving Chinese walls for maintaining the integrity of the competition."
An LU source added: "Clearly, we are aware of the issues that could arise, but these things happen whenever companies get together.