National officers from Unite, PCS and Prospect met Mr Nelson on Wednesday. They made clear their unified opposition to the proposed changes which will see the final salary pension scheme closed to new entrants from December 1.

Mr Nelson was told very clearly and in very direct terms that BAA's decision had no financial foundation.

The unions said the scheme was healthy and that changes must, therefore, be a cost cutting measure at the workforce's expense.

Brendan Gold, Unite national secretary for civil air transport, who chaired the union side of the meeting said: "The unions are not prepared to accept a reduction in BAA's pension provision. "We told the chief executive that the company’s decision is unacceptable. Unions will mount a vigorous campaign industrially, politically and publicly to ensure this decision is reversed."

Ben Middleton, Prospect negotiations officer, said:"The decision to close the scheme is a fundamental breach of trust and confidence which will be damaging to industrial relations in BAA."