Labour's Albert Owen has been returned as the MP for Ynys Mon, defeating Plaid Cymru's hopes in its top target seat.
Ceredigion Lib Dem Mark Williams and Labour's Albert Owen in Ynys Mon
Plaid suffered another blow when party director of policy Simon Thomas was defeated by the Liberal Democrats in Ceredigion.
There were angry exchanges after the Ynys Mon declaration in Llangefni as independent and former Tory AM Peter Rogers condemned Plaid's campaign.
Labour won with an increased majority of 1,242 over Plaid.
Mr Owen said jobs and the island's economy had been central to his campaign. But Plaid's candidate Eurig Wyn said the area faced massive problems.
Mr Rogers provoked angry exchanges when he spoke, telling the crowd: "We have seen the diminishment of Plaid Cymru here.
"They are the most arrogant people to speak to on the doorsteps," he added, leading to shouts.
Speaking to the BBC Wales news website, Mr Rogers said: "Of course, I'm disappointed".
He blamed the opinion polls for his loss, and said said tactical voting had affected him.
"Everybody is desperate in Anglesey for Plaid not to come back again. Some of these people are absolutely appalling.
"I've never met supporters like them. I'm very pleased that they're losing seats in Wales".
Police then provided an escort for Mr Rogers and his family to leave the Plas Arthur Leisure Centre in Llangefni, as a handful of protestors outside slow handclapped him.
Former Plaid Cymru leader Dafydd Wigley, said Eurig Wyn, a former MEP, had "slogged his guts out" and it was a "matter of regret" that he had not won.
"It seems to me it was the intervention of Peter Rogers that made a difference," Mr Wigley said. "It's a disappointment, but we fight on".
Labour MEP Glenys Kinnock said: "For us, it was a very very good result... Albert Owen has a very good following".
Mr Owen won with 12,278 votes - a majority of just over 1,200. In 2001 he had had a majority of 800.
Plaid's Adam Price, who retained his seat in Carmarthen East and Dinefwr, more than doubling his majority to over 6,700, said the loss of Simon Thomas was a huge blow, but politics was a cruel game.
And Elfyn Llwyd, Plaid's parliamentary leader said it had been a "challenging" election for his party. He said that in the 2007 assembly elections Plaid Cymru would be looking to govern Wales.