The Conservativesand Labour are "jointly responsible for the current economic crisis," says Plaid Cymru MP Elfyn Llwyd.
He was speaking at the close of the Welsh nationalist party's annual conference in Llandudno on Saturday.
Llwyd, Plaid Cymru’s leader at Westminster, attacked the "London parties" for proposing cuts in public spending.
“We mustn’t forget that the Tories are jointly responsible for the current economic crisis either," he said.
"They have consistently voted to let the market run wild, promoting a culture of financial risk and irresponsibility.
“The state of the economy has been the making of New Labour and the Conservatives argue about planned cuts in public expenditure."
Llwyd claimed that Plaid "can think differently" and come up with practical solutions.
“The London parties have been taking the people of Wales for a ride for long enough," he said.
"If the London parties are so good then how come Wales is still 20 per cent poorer than the rest of the UK?
"It’s time to end the old boys club in London who are simply governed by their party whips, and fight for justice for the people of Wales.”
In a fraternal address, SNP Commons leader Angus Robertson said that "only a strong nationalist voice at Westminster" will protect Scotland and Wales from spending cuts.
“Both the Tory and Labour parties are following a cuts agenda," he said.
"In Wales and Scotland the only protection is a strong Plaid Cymru and a strong SNP - the only parties that always stand for Wales and Scotland.
“At the next Westminster election we need to elect a record number of Plaid and SNP MPs to form a Celtic bloc, a block on cuts and services like the NHS, a block on financial attacks to the Welsh Assembly and Scottish Governments and strong force in Parliament that stands up for the real priorities of people in Wales and Scotland."

Dods Parliamentary Communications Ltd