Plaid Cymru made the comments as Wrexham MP Ian Lucas hosted a meeting with one of the Labour leadership contenders Ed Miliband to win support locally.
Cllr Marc Jones, leader of the Plaid group on Wrexham Council, said:
"It's always welcome that Labour joins the broad campaign to improve the lot of low-paid workers. The Living Wage has won a lot of support in Wales and much of the credit for that is down to TCC, the campaigning community charity based in Wrexham.
"Back in 2007 Plaid supported the TCC and Unison campaign to introduce a Living Wage in the Assembly and Plaid locally has also played a part - again alongside Unison - in pushing the local council to raise the two lowest pay bands as a step towards a Living Wage. Labour councillors voted against that agreement.
"The question I'd ask of Ian Lucas and Ed Miliband is why they didn't see fit to introduce this Living Wage when they had the chance during their 13 years in power in London? Labour lost power because it deserted working-class people and trying to jump on this bandwagon so late in the day is pure hypocrisy."
He added that the Welsh Assembly already has a Living Wage policy for all staff, so everyone is paid at least 15% more than the existing minimum wage. Cllr Jones added that the London Assembly had also introduced a similar scheme for its workers as had Manchester City Council.