Plaid Cymru's director of elections Helen Mary Jones has said a vote for the nationalists would herald "a fresh start" for Welsh politics.
Mrs Jones said only Plaid Cymru candidates were not answerable to party bosses in London, and blamed the major parties for "corruption and rottenness" in parliamentary politics.
She said: "While so many of the issues that affect our communities and our day-to-day lives, like pensions and benefits, and the massive issues like war and peace, are still decided in Westminster, it's really important to have Plaid Cymru MPs there.
"Plaid Cymru MPs are the only MPs in Wales who only answer to the people of Wales. All the rest, in the end, whatever they say, have to answer to their bosses in London.
"That's why in this election, we're asking people in communities across Wales to think about it: do they want more of that same old politics? Do they want more of the parties that allowed this corruption and rottenness to happen in the first place?
"Or do they want a fresh start with an MP who only answers to them? If that's what we want, then our only option is to vote Plaid."