M&E union Amicus is to push ahead with a ballot of its members for industrial action over the issue of travel pay on the Heathrow Terminal 5 site in west London.

Amicus is furious that, under a deal negotiated with client BAA and Laing O’Rourke, more than 3000 building workers on the site currently receive £25 a day extra for travelling time to the site – whereas M&E workers do not.

A meeting on Wednesday between the union and BAA resulted in stalemate, with BAA telling Amicus to take the issue to the project’s discussion forum for industrial relations.

However, Amicus claims that the issue is not a matter for the forum, as the travel pay deal falls out of the forum’s remit.

Frank Westerman, Amicus’ regional organiser, said that it was not right that Laing O’Rourke could operate outside the agreed national pay arrangements to negotiate separate travel pay. He said: “T5 is a logistical nightmare to travel around on its own, and it is only right that M&E workers should be on the same travel pay arrangements as other workers on the site.”

It is understood that if BAA implemented the additional pay for the M&E sector, for contractors such as Amec, Crownhouse and Balfour Kilpatrick, it would cost BAA an extra £12-14m in total.

BAA said it would be “surprised and disapointed if Amicus rushed to an industrial ballot”. A spokesperson said this move would be “unjustified and out of line with the constitutional arrangements covering the major projects agreement for the site.”

She said: “It would be unjustified because this matter was negotiated to agreement in joint negotiations. It would be unconstitutional as Amicus has not allowed the T5 joint council to refer this matter to the major projects agreement forum, which is required under the major projects agreement.”