Elfyn Llwyd says the UK debates put Plaid Cymru at a 'gross disadvantage'
Plaid Cymru is seeking legal advice over plans for TV election debates between the main UK party leaders.
Plaid's leader at Westminster wants the Electoral Commission to examine plans for debates between Gordon Brown, David Cameron and Nick Clegg.
There will be separate debates held in Scotland, Wales and Northern Ireland.
But Elfyn Llwyd said it did not matter what "might or might not be cobbled together in the future to appease us in Wales... we've been left out."
The first of the 90-minute programmes, with Labour Prime Minister Gordon Brown, Conservative leader David Cameron and Liberal Democrat leader Nick Clegg will be on ITV, the second on Sky and the third on the BBC.
ITV's Alastair Stewart will host the first, Sky's Adam Boulton the second and the BBC's David Dimbleby will host the third debate.
The format will be the same for each, although about half of each debate will be themed.
The leaders of the main UK political parties agreed to three TV debates
But Mr Llwyd said he thought the plans placed his party at a "gross electoral disadvantage".
He said: "As it stands at the moment, it is unfair because it places us at an electoral disadvantage, come what may.
"We are targeting a UK-wide audience because there are people from over the border who vote for Plaid Cymru and a lot of people within Wales receive network television rather than BBC Wales so, therefore, it is a disadvantage.
"We are represented in Westminster and have been for decades. We play a full part in political life in Westminster each and every day that the place is sitting.
"To be excluded in this way, and to have some idea that "in the future something will be cobbled together" - sorry, it's not good enough."
The BBC's chief political adviser, Ric Bailey, said the announcement on the UK-wide programmes was needed to establish the principle of the debates before the BBC could say what was needed to ensure the impartiality of its role.
Mr Llwyd said: "It's as clear as mud. We don't know how many programmes, we don't know exactly who [will be taking part], we don't know how long they'll be.
"It seems to have been put together overnight and rushed out."