SIPTU has called on the main opposition parties to spell out their position on offshore oil and gas policy in the light of the valuation of the Corrib gas field.
The union's national offshore committee also called on political parties to promise they would halt the outsourcing of offshore oil and gas jobs, goods and services. It would like to see policies that foster the creation of a lucrative native Irish oil and gas industry.
The offshore committee quotes a 1998 report by international oil and gas consultants Wood MacKenzie, which puts the size of the Corrib field off Mayo at seven trillion feet of gas.
It says that this is estimated to be worth €21 billion.
"This massive amount, and the presence of many other potential prospects around our shores, was handed over to the oil companies under legislation introduced by Ray Burke, in 1987, formerly minister for energy, and was improved upon by Bobby Molloy in 1992," Mr Pádraig Campbell, the committee's spokesman, said.
"It could and should be a huge source of revenue to the Irish economy for much-needed areas such as health, schools, infrastructural development and pension provision."
The union has also condemned a proposal by the Progressive Democrats to sell off the State's main ports. The proposal, in the party's election manifesto, is "ludicrous,particularly for an island nation", the committee says.
The union expresses disappointment at "the ambiguous response from the Taoiseach, Mr Ahern, in relation to this proposal and the other privatisation proposals, including the sell-off of An Bord Gáis and the ESB (two State companies already linked to the Corrib field give-away)".
"The opposition parties have yet to comment on the cynical politically motivated diverting of the gas pipeline from the Corrib field, at taxpayers' expense, to Galway when Galway is already due to get gas from the Dublin-to-Galway gas line."
The union believes the new government should introduce a windfall tax on oil company offshore profits, similar to that recently introduced in Britain at a rate of 10 per cent.
Last month, Dr Jerry Cowley, who is running as an Independent in the Mayo constituency, called for a renegotiation of the State's deal with Enterprise Energy Ireland on the Corrib gas field, following its multi-billion euro takeover by Royal Dutch/Shell.
Dr Cowley described the current deal as a disgrace and said the £4.3 billion sterling valuation placed on Enterprise Oil by Royal Dutch/Shell indicated the Corrib field project had been undervalued.
The Sinn Féin candidate in Mayo, Mr Vincent Wood, also said the people of Mayo had "been sold a pup by this Government" on the issue of the provision of Corrib gas to the county.
He was commenting on the announcement by the Minister of State for energy, Mr Joe Jacob, that towns on the Galway-to-Dublin gas pipeline would connected to the grid.
The community in Erris, which had objected to the siting of a gas terminal for the Corrib project, had been "sidelined and ignored", Mr Wood added.
A decision on the Bord Pleanála hearing into the terminal is not due until after the election.